著者
HOHENEGGER Cathy KORNBLUEH Luis KLOCKE Daniel BECKER Tobias CIONI Guido ENGELS Jan Frederik SCHULZWEIDA Uwe STEVENS Bjorn
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.2020-005, (Released:2019-11-10)
被引用文献数
1

Basic climate statistics, such as water and energy budgets, location and width of the InterTropical Convergence Zone (ITCZ), trimodal tropical cloud distribution, position of the polar jet and land-sea contrast remain either biased in coarse-resolution General Circulation Models or are tuned. Here we examine the horizontal resolution dependency of such statistics in a set of global convection-permitting simulations integrated with the ICOsahedral Non-hydrostatic (ICON) model, explicit convection and grid spacings ranging from 80 km down to 2.5 km. The impact of resolution is quantified by comparing the resolution-induced differences to the spread obtained in an ensemble of eight distinct global storm-resolving models. Using this metric, we find that, at least by 5 km, the resolution-induced differences become smaller than the spread in 26 out of the 27 investigated statistics. Even for 9 (18) of these statistics, a grid spacing of 80 (10) km does not lead to significant differences. Resolution down to 5 km matters especially for net shortwave radiation, which systematically increases with resolution due to reductions in low cloud amount over the subtropical oceans. Further resolution dependencies can be found in the land-to-ocean precipitation ratio, in the latitudinal position and width of the Pacific ITCZ and in the longitudinal position of the Atlantic ITCZ. Also in the tropics, the deep convective cloud population systematically increases at the expense of the shallow one, whereas the partition of congestus clouds remains fairly constant. Finally, refining the grid spacing systematically moves the simulations closer to observations, but climate statistics exhibiting weaker resolution dependencies are not necessarily associated with smaller biases.
著者
STEVENS Bjorn ACQUISTAPACE Claudia HANSEN Akio HEINZE Rieke KLINGER Carolin KLOCKE Daniel RYBKA Harald SCHUBOTZ Wiebke WINDMILLER Julia ADAMIDIS Panagiotis ARKA Ioanna BARLAKAS Vasileios BIERCAMP Joachim BRUECK Matthias BRUNE Sebastian BUEHLER Stefan A. BURKHARDT Ulrike CIONI Guido COSTA-SURÓS Montserrat CREWELL Susanne CRÜGER Traute DENEKE Hartwig FRIEDERICHS Petra HENKEN Cintia Carbajal HOHENEGGER Cathy JACOB Marek JAKUB Fabian KALTHOFF Norbert KÖHLER Martin LAAR Thirza W. van LI Puxi LÖHNERT Ulrich MACKE Andreas MADENACH Nils MAYER Bernhard NAM Christine NAUMANN Ann Kristin PETERS Karsten POLL Stefan QUAAS Johannes RÖBER Niklas ROCHETIN Nicolas SCHECK Leonhard SCHEMANN Vera SCHNITT Sabrina SEIFERT Axel SENF Fabian SHAPKALIJEVSKI Metodija SIMMER Clemens SINGH Shweta SOURDEVAL Odran SPICKERMANN Dela STRANDGREN Johan TESSIOT Octave VERCAUTEREN Nikki VIAL Jessica VOIGT Aiko ZÄNGL Günter
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.2020-021, (Released:2020-01-28)

More than one hundred days were simulated over very large domains with fine (0.156 km to 2.5 km) grid spacing for realistic conditions to test the hypothesis that storm (kilometer) and large-eddy (hectometer) resolving simulations would provide an improved representation of clouds and precipitation in atmospheric simulations. At scales that resolve convective storms (storm-resolving for short) scales, the vertical velocity variance becomes resolved and a better physical basis is achieved for representing clouds and precipitation. Similar to past studies we find an improved representation of precipitation at kilometer scales, as compared to models with parameterised convection. The main precipitation features (location, diurnal cycle and spatial propagation) are well captured already at kilometer scales, and refining resolution to hectometer scales does not substantially change the simulations in these respects. It does, however, lead to a reduction in the precipitation on the time-scales considered – most notably over the Tropical ocean. Changes in the distribution of precipitation, with less frequent extremes are also found in simulations incorporating hecto-meter scales. Hectometer scales appear more important for the representation of clouds, and make it possible to capture many important aspects of the cloud field, from the vertical distribution of cloud cover, to the distribution of cloud sizes, to the diel (daily) cycle. Qualitative improvements, particularly in the ability to differentiate cumulus from stratiform clouds, are seen when reducing the grid spacing from kilometer to hectometer scales. At the hectometer scale new challenges arise, but the similarity of observed and simulated scales, and the more direct connection between the circulation and the unconstrained degrees of freedom make these challenges less daunting. This quality, combined with an already improved simulation as compared to more parameterised models, underpins our conviction that the use and further development of storm-resolving models offers exciting opportunities for advancing understanding of climate and climate change.