It is to be distributed to the modelling groups in order to evaluate model clouds and contribute to the model development process using observations from the new generation of space-borne sensors, e. Implementation of the new prognostic cloud scheme PC2 in the Unified Model. You might also like. Climate monitoring of the land and atmosphere Global observations of surface and upper air temperature and humidity, surface pressure and precipitation … Read more. Our scientists All our research and development is underpinned by scientists with a broad range of skills.
Read more. Water resources Understanding climate impacts on water resources at both the regional and global scale. Help us improve our website Take our short survey. Settings Temperature units. Miles per hour mph. Kilometres km. Please note that when changing units, only forecasts and maps will be affected. In the tropical to sub-tropical area, they all showed that upper clouds increase as climate becomes warmer but ice water path IWP decreases. Such cloud responses are different from other GCMs Tsushima et al.
Satoh et al. This mechanism was recently used by Bony et al. However, as described above, the NICAM results show an increase in upper clouds, so more detailed discussions are required to resolve this contradiction.
Chen et al. These studies raise the question of why such high-cloud responses occur and why the high-cloud responses of NICAM are different from those of the other GCMs.
Noda et al. Using this method, Noda et al. Such small-scale clouds are not generally explicitly represented by ordinary GCMs and parameterized by cloud macro-physics schemes such as cloud fraction, but they are explicitly represented in NICAM. These findings suggest that assumptions introduced in the cloud macro-physics schemes should be examined more closely and compared with explicit calculations using cloud microphysics schemes to understand the different responses of high clouds between models. Since deep convective circulations are explicitly represented by NICAM, future changes in cloud systems can be examined together with changes in meso-scale properties and their embedding synoptic structures.
TC changes were examined by Yamada et al.
They further examined the eye wall structures and showed that eye wall height tends to increase with TC intensity. Yamada and Satoh examined projected changes in ice and liquid clouds associated with TCs. These studies are based on the results of 5-month simulations, which are too short to explore basin-scale differences or inter-annual variabilities. Recently, however, Yamada et al. Using these simulation results, Satoh et al. Future changes in extra-tropical cyclones are examined by Kodama et al.
Their simulation shows that, similar to the TC response, the frequency of extra-tropical cyclones decreased but the cyclones slightly intensified on average. The storm track moved poleward, consistent with other GCMs. In the subsequent subsections, we review the outcomes of the SOUSEI program, the analysis of cloud size statistics, upper cloud changes, and extra-tropical cyclone changes in more detail. To explore the characteristic change in high clouds, we show the size distribution of high cloud in Fig.
Cloud sizes are shown as an equivalent radius of a circle, and thus, the minimum radius is approximately half of the model grid size Noda et al. Frequency distribution of high-cloud size. Adapted from Noda et al. Under the warmer condition, the number of clouds increases in all radius bins.
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In particular, smaller clouds increase in frequency more than larger clouds. The smaller clouds contribute more to the increase in the total high-cloud coverage under the warmer condition. Changes in OLR due to changes in high clouds directly affect projected changes to the global radiative budget. An overbar with a prefix i denotes an average over i th cloud area.
Those values are hereafter shown by being binned according to the cloud radius. In contrast, the contribution of T CT increases almost linearly, independent of cloud size, and eventually approaches a constant value. The net contributions of the two elements are comparable. The contribution of F CLR is one order smaller than that of the other elements.
Budget analysis of outgoing longwave radiation changes due to global warming. P denotes the probability distribution function of high cloud number. The original OLR values black , diagnosed values from Eq.
Hartmann and Larson claimed that T CT is kept almost constant, irrespective of surface temperature, which is referred to as the FAT hypothesis. In other words, whether the FAT hypothesis holds or not depends on which size of cloud primarily increases or decreases due to global warming. This suggests that the size distribution of high clouds should be examined for more reliable projections of radiation budget.
Clouds play an important role in the uncertainty of the climate projection under the global warming condition because of their influence on the energy balance of the atmosphere Hartmann et al. In particular, we focus on cloud ice simulations Waliser et al. The aim of their study was to reveal whether the responses of clouds, particularly high clouds, to global warming in NICAM simulations are robust irrespective of the choice of cloud microphysics schemes.
The global mean cloud feedback. Mark Zelinka. Adapted from Chen et al. This difference is consistent with the difference in cloud fraction response to global warming not shown. For NSW6-JJA, the cirrus cloud fraction significantly increases in the tropics and, as a result, the LW cloud feedback attributed to cirrus clouds are mostly dominant in the tropics.
In contrast, although the NDW6-JJA cirrus cloud fraction changes mainly in the tropics, appreciable changes occur in the mid-latitudes. This means that the LW cloud feedback from cirrus clouds dominate in the tropics, although they are non-negligible in the mid-latitudes. The zonal mean distribution of cloud changes. Note that the longwave cloud radiative feedback are calculated using the cloud radiative kernel proposed by Zelinka et al.
As described above, Chen et al. This result demonstrates the importance of ice cloud microphysics in making more accurate assessments of cloud radiative forcing. The present simulation was analyzed by Kodama et al. In this and the next subsections, we review future changes in cloud and precipitation and associated circulation changes, such as TCs and storm tracks, due to global warming using outputs of long-term NICAM simulations. NSW6 was utilized to explicitly calculate cloud microphysics without a cumulus parameterization scheme. A slab ocean model was utilized to simulate SSTs, which were nudged toward Taylor-corrected Taylor et al.
The high-cloud amount is increased, as shown by the upper panels of Fig. The decrease in the low-cloud amount is also related to an increase in cloud-top height due to warming SST. The reduction of the low-cloud amount is similarly seen in many conventional GCMs Zelinka et al. Panels represent high, middle, and low clouds from top to bottom. Under the future climate condition, the global averaged precipitation rate increased by approximately 1.
The distribution of zonal mean precipitation rates is shown in the right panels of Fig. The model projects that the precipitation rate is increased in the tropics, slightly decreased over the subtropics, and increased at the higher latitudes. An increase is prominent near ITCZ throughout all seasons.
The change in TC activities is documented in Satoh et al. Precipitation related to TCs has been investigated in previous studies Rodgers et al. The TC-rainfall rate is high over the subtropics during all seasons in both climate conditions right panels of Fig. This result is qualitatively consistent with observational studies Rodgers et al. Therefore, future change in TCs appears to contribute to the decrease in precipitation over the subtropical eastern North Pacific in the future climate simulation.
Results of the a present-day climate simulation — and b the future climate simulation — The panels follow the same seasons as defined in Fig. It is still unclear how clouds interact with large-scale circulation in the extratropics. Many studies using GCMs project a poleward shift of the storm track, a reduction in the total number of extratropical cyclones, and an increase in the number of intense extratropical cyclones due to global warming Geng and Sugi ; Yin ; Mizuta It has also been suggested that enhanced extratropical cyclone intensities due to global warming induce more SW cooling and more LW warming Tselioudis and Rossow In contrast, a poleward shift of the storm track does not seem to induce a significant positive SW cloud radiative effect in the southern hemisphere Grise and Polvani Much higher horizontal resolution is necessary to reproduce fine-scale structures of extratropical cyclones such as cold and warm fronts.