著者

Makoto Kondo Yousuke Sato Masaru Inatsu Yuta Katsuyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-012, (Released:2021-03-12)

被引用文献数

4

---

The performances of bulk microphysical schemes were evaluated through comparisons with observations, including a new volume scanning video disdrometer targeting one of a typical snowfall event in Hokkaido, Japan. For the evaluation, downscaling experiments using three bulk microphysical schemes were conducted: a two-moment bulk scheme, a one-moment bulk scheme, and an improved version of the one-moment bulk scheme coupled with an identical dynamical core. The two-moment scheme successfully simulated the measured relationship between particle size and terminal velocity distribution (PSVD). On the other hand, the one-moment scheme overestimated the graupel frequency, its terminal velocity, and underestimated the particle diameter. The improved version of the one-moment bulk scheme reduced the overestimation of the terminal velocity of hydrometeors, but still overestimated the graupel frequency. We improved the overestimation of terminal velocity and the frequency of graupel in the one-moment scheme by modifying the assumption of the velocity–diameter relationship and the intercept parameter of the size distribution of graupel based on the results of the new disdrometeor. The observation of the new disdrometer would give us hints to improve the microphysics schemes in snowfall cases.

著者

UNUMA Takashi TAKEMI Tetsuya

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2021-009, (Released:2020-11-30)

被引用文献数

8

---

In July of 2017 and 2018, heavy rainfall events occurred, leading to significant damage in Japan. This study investigated the rainfall characteristics and environmental conditions for these heavy rainfall events using rain intensity data from operational weather radars and mesoscale analysis data. An automatic algorithm was developed to categorize precipitating cloud systems into five types, one with weaker rainfall (less than 10 mm h−1) and four with stronger rainfall (greater than or equal to 10 mm h−1), i.e., quasi-stationary convective clusters (QSCCs), propagating convective clusters (PCCs), short-lived convective clusters (SLCC), and other convective but unorganized rainfall. The rainfall amount due to the weaker rainfall was found to dominate the total rainfall in most of the analysis region; however, the contribution from the stronger rainfall types became larger than that from the weaker rainfall type in regions that experienced heavy rainfall. Among the stronger rain types, SLCCs dominate over the rainfall contributions from QSCCs or PCCs, whereas rainfalls from convective but unorganized systems are very minor. It was emphasized that the contribution from stronger rains due to organized systems with areas of 200 km2 plays a major role in regions with significant amounts of rainfall during the heavy rainfall events examined here. The examination of the environmental conditions for the development of each system demonstrated that, from the viewpoint of moisture content, the stability conditions were more unstable in 2018 than in 2017. There is also a clear linkage in the time series between rainfall types and the environmental properties of precipitable water and vertical shear. It was found that both the column moisture content and the middle-to-upper-level relative humidity characterize the environmental conditions for the occurrence of the present heavy rainfall events. Features of the rainfall types and their environmental conditions were compared with the QSCC climatology.

著者

Hiroaki Kawase Munehiko Yamaguchi Yukiko Imada Syugo Hayashi Akihiko Murata Tosiyuki Nakaegawa Takafumi Miyasaka Izuru Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.17A, no.Special_Edition, pp.7-13, 2021 (Released:2021-01-28)

参考文献数

34

被引用文献数

20

---

Impacts of historical warming on extremely heavy rainfall induced by Typhoon Hagibis (2019) are investigated using a storyline event attribution approach with the Japan Meteorological Agency Nonhydrostatic Model (JMA-NHM). Control experiments based on JMA mesoscale analysis data well reproduce the typhoon's track, intensity, and heavy precipitation. First, two non-warming experiments are conducted: One excludes both 40-year atmospheric and oceanic temperature trends from 1980 to 2019, and the other excludes the oceanic trend only. A comparison between control and non-warming experiments indicates that historical warming strengthens typhoons and increases the amount of total precipitation by 10.9% over central Japan. The difference between CTL and non-warming experiments without both atmospheric and oceanic temperature trends is larger than that without just the oceanic trend (7.3%). Additional sensitivity experiments without Japan's topography indicate that topography enhances not only total precipitation but also the changes in total precipitation due to historical warming. Through the storyline event attribution approach, it is concluded that historical warming intensifies strength of Typhoon Hagibis (2019) and enhances the extremely heavy precipitation induced by the typhoon.

著者

Kuniyasu Sugawara Masaru Inatsu Seiji Shimoda Keach Murakami Tomoyoshi Hirota

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2021-004, (Released:2021-01-04)

被引用文献数

4

---

While global warming may expand suitable places for potato cultivation in cold regions, it may reduce the yield due to the increase of hot days during the tuber growth period. This study evaluated the effects of global warming on potato cultivation over Hokkaido by dynamically-downscaled ensemble experiments called d4PDF and assessed applicability of possible adaptive measures. In this study, we define the suitable area based on the accumulated temperature and deduced a relationship between the potato yield per unit area and the number of hot days (maximum temperature > 28°C) from crop statistic data. In a warming environment with 2K or 4K increase in global-mean temperature relative to the present climate (1981-2010), the accumulated temperatures likely satisfied the criterion on potato production almost over Hokkaido. The risk of growth delay due to cold weather was projected to reduce. However, hot days in the tuber growth period would increase, reducing potato yield by 7% in a plus 2-K climate and 16% in a plus 4-K climate. This risk of yield loss would not be avoidable by moving up planting by 30 days, and the development of varieties that are tolerant to 31-33°C would be a possible way to adaptation.

著者

Satoshi Iizuka Ryuichi Kawamura Hisashi Nakamura Toru Miyama

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.17A-004, (Released:2020-12-21)

被引用文献数

11

---

Typhoon Hagibis (2019) caused widespread flooding and damage over eastern Japan. The associated rainfall maxima were primarily observed on the windward mountain slopes along with the west of the leading edge of a low-level front. Concomitantly, a significant positive value in sea surface temperature anomalies (SSTAs) was observed in association with an ocean eddy over the Oyashio region, together with anomalous warmth over the entire western North Pacific. The present study examines the role of the SSTAs in the rainfall distribution associated with Hagibis, to deepen our understanding of the influence of the midlatitude ocean on tropical cyclones and associated rainfall. Our sensitivity experiments demonstrate that the observed warm SSTAs had the potential to displace the rainfall caused by Hagibis inland and thereby acted to increase precipitation along the Pacific coast of northeastern Japan. Our results suggest that midlatitude SSTAs on ocean-eddy scales can also influence the synoptic-scale atmospheric front and associated heavy rainfall.

著者

Yasutaka Hirockawa Teruyuki Kato Kentaro Araki Wataru Mashiko

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-044, (Released:2020-12-10)

被引用文献数

37

---

In early July 2020, an extreme rainfall event generated precipitation exceeding 1000 mm in Kyushu district, southwestern Japan. Especially, an elongated and stagnated mesoscale convective system formed around the Kuma River in central Kyushu district produced localized heavy rainfall with precipitation over 600 mm in 13 hours. Characteristics of this extreme rainfall event were investigated using distributions of radar/raingauge-analyzed precipitation amounts (RAP) that were statistically compared with those during the warm seasons (April–November) in 2009-2019. The results are as follows: (1) nine heavy rainfall areas of linear-stationary type (LS-HRAs) were extracted, (2) spatial and temporal scales of two LS-HRAs among the nine exceeded 270 km and 10 hours, respectively, (3) the maximum RAP exceeding 100 mm in LS-HRAs were comparable to those in previous extreme rainfall events, (4) large accumulated three-hour precipitation amounts exceeding 200 mm were more frequently observed than those in previous events, and (5) the accumulated five-day precipitation amount integrated around Kyushu Island was the largest since 2009. This study also showed that a large area-integrated precipitation amount was produced mainly from widespread precipitation systems associated with the Baiu front, while the nine LS-HRAs significantly contributed to localized heavy rainfall.

著者

Pradeep Khatri Hiroaki Ooashi Hironobu Iwabuchi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.228-232, 2020 (Released:2020-12-05)

参考文献数

39

被引用文献数

5

---

Aerosol effects on deep convective cloud (DCC) have been recognized as one of the complex subjects in climatic studies because of the difficulty in quantifying the sole effect of aerosols on DCC. The complexity further arises if the atmosphere has very strong temporal and spatial variations such as that of Indo-Pacific Warm Pool (IPWP) region. Considering the strong influence of IPWP region on global climate change and water circulation, we investigated aerosol effects on DCC over this region by using data of 2015-2016 El Niño and the 2017-2018 La Niña events. We developed a spectral analysis based framework to identify and decouple the influences of major external factors on aerosol-DCC relationship. We found that temporal variations of aerosols, clouds, and meteorology longer than 2 days' time scale can have larger influences than their diurnal and spatial variations on aerosol-DCC relationship. By removing the effects of those spatial and temporal variations of different scales, the study suggests that aerosols of IPWP region can affect DCC properties with time lags less than ∼5 hours and by increasing cloud-top height, cloud coverage, and DCC number concentration with the increase of aerosols.

著者

Yu Li Shuqing Ma Ling Yang Xiaoqiong Zhen Dan Qiao

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-042, (Released:2020-11-23)

---

Array weather radar (AWR), a kind of distributed phased array radar, includes at least three Phased Array Front Ends (PAFE). Every three PAFEs are grouped for synchronous scanning to ensure that the Data Time Difference (DTD) at the same point in the fine detection area is less than 2 s. This paper adopts the multiple-Doppler wind synthesis method to synthesize the wind field of the small-DTD AWR data and discusses the sensitivity analysis on the wind fields under the different DTDs. The analysis experiment includes the wind fields under two types of precipitation systems. One is a convective precipitation system with unstable airflow, and the other is a non-convective precipitation system with stable airflow. The statistical analysis showed that, due to the advection effect and intrinsic evolution of the precipitation systems, the bigger the DTD is, the bigger the wind field error is. When the DTD is greater than 24 s, the wind field obtained by the convective precipitation system has more errors. When the DTD is greater than 84 s, the wind field obtained by the non-convective precipitation system has more errors.

著者

Katsuya Yamashita Satoru Yamaguchi Takayuki Saito Yuya Yamakura Eiichiro Kanda Sento Nakai Hiroki Motoyoshi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-045, (Released:2020-11-23)

---

A system with existing snowfall sensors, which is used to control the operation of the sprinkler snow removal system, was developed to acquire data that can be used to generate snowfall distribution with high spatiotemporal resolution. This had advantages such as low installation and management costs, as well as flexibility with respect to the configuration of its observation points. The results confirmed that this system, developed for experimental purposes in Nagaoka City (Niigata Prefecture), made it possible to generate the snowfall amount distribution as well as the precipitation rate within a 25 km × 30 km area at 10-min intervals based on in-situ measurements conducted at 16 ground-based points. A comparison of the system with other observation systems confirmed that it could detect detailed spatial snowfall variations, which could not be achieved using existing the ground-based observation networks, and provide sufficient observation accuracy for winter road management. Since many snowfall sensors are installed on the Sea of Japan side of mainland of Japan, this system has the potential for extensive application in the snowy areas of Japan characterized by heavy snowfall at temperatures of approximately 0°C.

著者

Pradeep Khatri Hiroaki Ooashi Hironobu Iwabuchi

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-038, (Released:2020-10-22)

被引用文献数

5

---

Aerosol effects on deep convective cloud (DCC) have been recognized as one of the complex subjects in climatic studies because of the difficulty in quantifying the sole effect of aerosols on DCC. The complexity further arises if the atmosphere has very strong temporal and spatial variations such as that of Indo-Pacific Warm Pool (IPWP) region. Considering the strong influence of IPWP region on global climate change and water circulation, we investigated aerosol effects on DCC over this region by using data of 2015-2016 El Niño and the 2017-2018 La Niña events. We developed a spectral analysis based framework to identify and decouple the influences of major external factors on aerosol-DCC relationship. We found that temporal variations of aerosols, clouds, and meteorology longer than 2 days' time scale can have larger influences than their diurnal and spatial variations on aerosol-DCC relationship. By removing the effects of those spatial and temporal variations of different scales, the study suggests that aerosols of IPWP region can affect DCC properties with time lags less than ∼5 hours and by increasing cloud-top height, cloud coverage, and DCC number concentration with the increase of aerosols.

著者

MIYAMOTO Yoshiaki SATO Yousuke NISHIZAWA Seiya YASHIRO Hisashi SEIKI Tatsuya NODA Akira T.

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-051, (Released:2020-07-09)

被引用文献数

1

---

This study proposes a new energy balance model to determine the cloud fraction of low-level clouds. It is assumed that the horizontal cloud field consists of several individual cloud cells having a similar structure. Using a high–resolution simulation dataset with a wide numerical domain, we conducted an energy budget analysis. It is shown that the energy injected into the domain by surface flux is approximately balanced with the energy loss due to radiation and advection due to large–scale motion. The analysis of cloud cells within the simulated cloud field showed that the cloud field consists of a number of cloud cells with similar structures. We developed a simple model for the cloud fraction from the energy conservation equation. The cloud fraction diagnosed using the model developed in this study was able to quantitatively capture the simulated cloud fraction.

著者

OHNO Tomoki NODA Akira T. SATOH Masaki

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-054, (Released:2020-07-20)

被引用文献数

7

---

The impacts of the saturation adjustment type approach to sub-grid-scale (SGS) ice clouds in a turbulent closure scheme on the high clouds and their response to global warming were investigated based on the radiative–convective equilibrium experiments (RCEs). This was motivated by the fact that the time scale of ice condensation is several orders of magnitude longer than that for liquid water. The RCEs were conducted with uniform sea surface temperatures over the spherical domain for the Earth's radius without rotation using an explicit cloud microphysics and a non-hydrostatic icosahedral atmospheric model. This study revealed that suppressing the phase change effect associated with the SGS ice condensation on the buoyancy of the SGS turbulence could cause approximately a 20 % reduction of the total high cloud covers and a significantly different response of high cloud amounts to global warming due to the change in static stability near high clouds, which leads to weaker vertical heat transport at a sub-grid scale there. Since the typical value of the time scale of the ice-phase cloud is much longer than that for liquid water and the ice supersaturation is in general, using the saturation adjustment type approach for SGS ice clouds could lead to an overestimation of the effect of ice condensation for the turbulent mixing and model biases in simulations with both cloud resolving models and general circulation models. The present result underlines the critical nature of the treatment of SGS ice clouds in turbulence schemes which reflects a realistic ice condensation time scale not only for a better representation of high clouds in the current climate but for an improved projection of changes of high clouds due to global warming.

著者

WANG Chung-Chieh LIN Kuan-Yu DAVIS Christopher A. HUANG Shin-Yi LIU Stefano Chih-Shin TSUBOKI Kazuhisa JOU Ben Jong-Dao

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-036, (Released:2020-04-20)

被引用文献数

2

---

In this study, the impacts of Typhoon Morakot (2009)'s vortex structure on the extreme rainfall in Taiwan are investigated through an application of piecewise potential vorticity (PV) inversion. The control (CTL) experiment, starting at 0000 UTC 7 August or 15 h before landfall, reproduces the event realistically and is validated against the observations. By altering the PV perturbation inside 750 km from its center, we conduct sensitivity experiments in which the size and/or circulation strength of Morakot is reduced/weakened in the initial field in several different ways.  In the sensitivity tests, particularly those where the initial PV within the inner core (≤ 250 km) is significantly weakened, the storm makes landfall earlier, stays over land longer, and exits Taiwan later. Such track changes are accompanied by a contraction and spin-up of the inner core at early stages of the integration, caused by convection/latent heating within the inner core under large-scale low-level southwesterly flow. As a result, Taiwan receives an overall rainfall amount either comparable to, or even more than (up to +12 %), CTL in all tests. Thus, a weaker Morakot does not necessarily lead to less total rainfall over Taiwan, and the strong southwesterly flow and its moisture supply were bigger factors than the vortex structure in this event.   On the other hand, the rainfall in the southern Central Mountain Range on 8 August, which were the most-rainy area and period in reality, tended to decrease by up to 40 % with the contraction and a weaker outer circulation. Thus, the rainfall patterns and evolution in the sensitivity tests are considerably different than those in CTL, indicating that the vortex structure plays an important role in the rainfall of this region.

著者

Keita Fujiwara Ryuichi Kawamura Tetsuya Kawano

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.151-156, 2020 (Released:2020-08-09)

参考文献数

22

被引用文献数

5

---

This study investigated the remote impact of an increase in latent heat flux (LHF) over the Kuroshio on tropical cyclone (TC) development, using a cloud-resolving model. A control run and a sensitivity experiment with Kuroshio's LHF artificially enhanced were performed for Typhoon Chaba in 2010. The TC development simulated in the sensitivity experiment was suppressed as compared with the control run. The sensitivity experiment demonstrated that eyewall convection and the associated TC secondary circulation were suppressed by a decrease in equivalent potential temperature (θe) around the eyewall through the lower θe penetration into the inner core region in the boundary layer. The dynamic features of the TC were also altered by the attenuated TC secondary circulation through the inhibition of the inward advection of the absolute angular momentum. The super-gradient tangential velocities in the inner core were smaller than those in the control run. Such thermodynamic and dynamic changes were remotely induced by the decrease in moisture import from the Kuroshio. Since the increased LHF facilitated the development of a surface low over the Kuroshio, the intensified low further accumulated the Kuroshio's vapor and suppressed low-level northeasterlies toward the TC, resulting in interrupting the moisture import into the TC.

著者

Sujeong Lim Hyo-Jong Song In-Hyuk Kwon

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.145-150, 2020 (Released:2020-08-09)

参考文献数

20

被引用文献数

1

---

One way of the tropical cyclone (TC) initialization is assimilating the official advisory sea-level pressure observation to specify the initial structures of a TC with the aid of a background error covariance (BEC). In the hybrid four dimensional ensemble-variational data assimilation system, a static BEC explains the geostrophic and cyclostrophic wind-mass balance, and an ensemble BEC expresses the flow-dependent feature. Assimilation of the minimum sea-level pressure using a larger localization length-scale with limited ensemble members yields the closest to the observations at the initial state, but an imbalance in the broad analysis increment distorts geopotential and wind fields. Moreover, the reduced central pressure of TC is rapidly returned to an intensity that a model resolution can represent during the prediction. We introduce the application of final-scale localization (FSL) at the last outer loop with the shortest one to improve the TC initialization. With the aid of FSL, we may conduct the shorter localization length-scale, especially adopted for the TC initialization. As preliminary results, both analysis and prediction become more stable and the large-scale environments are preserved better than in the control experiment.

著者

Hyunuk Kim Baek-Jo Kim Hyoung-Gu Nam Jonghyeok Jeong Jae-Kwan Shim Kyu Rang Kim Seungbum Kim

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.140-144, 2020 (Released:2020-08-08)

参考文献数

35

被引用文献数

3

---

In this study, based on the daily maximum wind speed and maximum instantaneous wind speed data recorded at 61 observation points operated by the Korea Meteorological Administration from 1993 to 2018, the self-organizing map clustering method was used to classify regions with similar characteristics of strong wind and gust wind occurrence and intensity. Characteristics of these regions were analyzed by averaging 30 variables related to wind for each cluster. As a result, 13 homogeneous regions of strong wind and gust wind in Korea were identified, which were clearly divided into regions of high and low strong wind frequency of occurrences. In most regions, the average daily maximum wind speed and maximum instantaneous wind speed were high in spring and winter. However, the average daily maximum wind speed and maximum instantaneous wind speed exceeding the criteria of strong wind (14 m s−1) and gust wind (20 m s−1) in this study were high in summer and autumn. Among the four clusters with high occurrence of strong wind and gust wind, one was classified as a specific region with high occurrence in summer and autumn. This results are likely to be beneficial to support regional customized special weather reports and disaster prevention.

著者

Sheau Tieh Ngai Hidetaka Sasaki Akihiko Murata Masaya Nosaka Jing Xiang Chung Liew Juneng Supari Ester Salimun Fredolin Tangang

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.132-139, 2020 (Released:2020-08-08)

参考文献数

60

被引用文献数

9

---

The Non-Hydrostatic Regional Climate Model (NHRCM) was used in simulating the present and future rainfall climate over Malaysia under the RCP8.5 scenario in this study. Simulation and projection from 1979 to 2002 for present day and 2070 to 2100 for the end of century were conducted over the Malaysia. The 20 km resolution MRI-AGCM3.2 model simulation from Meteorological Research Institute (MRI) was used as boundary conditions. The objective of this study was to estimate the extreme rainfall projections in Malaysia at 5 km of resolution during the November to February period, representing the northeast monsoon season. Overall, the model was capable to simulate the historical rainfall climatology and distribution, but model tended to underestimate high rainfall frequency and mean rainfall intensity in Malaysia. However, compared with simulations at 25 km, added values have been shown at 5 km resolution. Based on the NHRCM05 simulations, a number of hotspots have been identified with significant projected increases up to 80% for the extreme rainfall indices (R20mm, RX1day, R95pTOT and R99pTOT), 30% increases in mean rainfall intensity (SDII) and 20% for consecutive dry days indices (CDD).

著者

Takafumi Miyasaka Hiroaki Kawase Tosiyuki Nakaegawa Yukiko Imada Izuru Takayabu

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.125-131, 2020 (Released:2020-07-23)

参考文献数

25

被引用文献数

14

---

Heavy precipitation in Japan is caused by various phenomena, such as tropical cyclones and the Baiu front, and shows regional-scale variation. Here we investigate extremely heavy precipitation events exceeding the 100-year return period in the Kanto area and future projections of such events using large ensemble climate simulations for periods of several thousand years. To understand these extreme events, associated sea level pressure anomalies over Japan and the surrounding region are classified into four clusters. These cluster means are characterized by (1) a strong anomalous cyclone, (2) a weak anomalous cyclone, (3) an anomalous cyclone accompanied by an anomalous anticyclone to the north, and (4) an anomalous anticyclone to the north. The cluster with a strong anomalous cyclone is accompanied by widely distributed heavy precipitation, and its area-averaged precipitation is predicted to be more enhanced under global warming than that of other clusters, partly because of an increase in the strength of strong tropical cyclones approaching Kanto. The cluster dominated by an anomalous anticyclone is characterized by localized heavy precipitation in the plains area. The relative frequency of this cluster will increase, whereas that of other clusters will decrease under global warming.

著者

Atsushi Inagaki Yovita Wangsaputra Manabu Kanda Meral Yücel Naoyuki Onodera Takayuki Aoki

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.120-124, 2020 (Released:2020-07-23)

参考文献数

18

被引用文献数

2

---

The similarity of the turbulence intensity profile with the inner-layer (i.e. from the ground to the top of the logarithmic layer) and the outer-layer (i.e. from the top of the inner layer to top of the boundary layer) scalings were examined for an urban boundary layer using numerical simulations. The simulations consider a developing neutral boundary layer over realistic building geometry with and without a slightly upsloping terrain. The computational domain covers an 19.2 km by 4.8 km and extends up to a height of 1 km, and is resolved by 2-m grids. Several turbulence intensity profiles are defined locally in the computational domain. The inner- and outer-layer scalings work well reducing the scatter of the turbulence intensity within the inner- and outer-layers, respectively, regardless of the surface geometry. Although the main scatters among the scaled profiles are attributed to the mismatch of the parts of the layer (i.e. inner or outer) and the scaling parameters, their behaviours can also be explained by introducing a non-dimensional parameter which consists of the ratio of the inner- and outer-layer parameters for length (the boundary-layer height over the roughness length), or velocity (the external free stream velocity over the friction velocity).

著者

Rimpei Kamamoto Kenji Suzuki Tetsuya Kawano Hiroshi Hanado Katsuhiro Nakagawa Yuki Kaneko

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.115-119, 2020 (Released:2020-07-04)

参考文献数

12

---

Two products from the Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR) algorithms, a flag of intense solid precipitation above the −10°C height (“flagHeavyIcePrecip”) and a classification of precipitation type (“typePrecip”) were validated by ground-based hydrometeor measurements and X-band multi-parameter (X-MP) radar observations of snow clouds on 4 February 2018. Contoured frequency by altitude diagrams of the X-MP radar reflectivity exhibited a significant difference between footprints flagged and unflagged by the “flagHeavyIcePrecip” algorithm, which indicated that the algorithm is reasonable. The hydrometeor classification (HC) by the X-MP radar, which was confirmed by microphysical evidence from ground-based hydrometeor measurements, suggested the existence of graupel in the footprints with “flagHeavyIcePrecip”. In addition, according to the information of the GPM DPR, the “flagHeavyIcePrecip” footprints were characterized by not only graupel but also large snowflakes. According to the information of X-MP radar HC, the “typePrecip” algorithm by the detection of “flagHeavyIcePrecip” was effective in classifying precipitation types of snow clouds, whereas it seems that there is room for improvement in the “typePrecip” algorithms based on the extended-DPRm-method and H-method.