Land-ocean Contrast Research Articles

Radiative heating and upwelling by different types of TTL clouds over the tropical convective regions

Tropical tropopause layer (TTL) clouds, defined as clouds whose tops are located above the tropopause level, play important roles in Earth's radiation balance and troposphere-to-stratosphere transport. Examining how different TTL cloud type gives influence on the radiative heating, we classified TTL clouds into three types (i.e., deep convective cloud, optically thick convective anvil cloud, and optically thin cirrus cloud) over the convectively active four tropical regions (i.e., Central Africa and South America continental regions and the Central and Western Pacific oceanic regions), using the combined Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and CloudSat data. Using the classified cloud data, we first examined characteristics of the macrophysical and microphysical properties of the classified cloud types. Amongst three types of TTL clouds over selected four regions, thin cirrus clouds are most abundant (almost four-fifths), and approximately 7% and 17% of TTL clouds are deep convective cloud and thick convective anvil clouds, respectively. It is noted that the land–ocean contrast in TTL clouds appears weak in spite of well-known land–ocean contrast in the convection intensity, suggesting that TTL cirrus clouds may be dominated by in situ cirrus clouds. We further examined radiative heating over the TTL altitudes by each cloud type and the associated radiatively-driven upwelling motion. It is revealed that the dominant contribution to the overall radiative heating is from thin cirrus clouds (∼48.4%) because of their abundance. Nevertheless, convective anvil clouds and deep convective clouds are also found to give significant contribution to the radiative heating. Such cloud radiative heating tends to lower the level of zero net radiative heating rate found in the clear sky by ∼400–900 m. The TTL clouds play an important role in the secondary circulation in the TTL by inducing the upwelling motion throughout the TTL, supporting the mechanism that the radiative effect of TTL clouds can enhance the mass flux from the troposphere to the stratosphere.

Assessing the performance of satellite derived and reanalyses data in capturing seasonal changes in extreme precipitation scaling rates over the Indian subcontinent

Intensity and frequency of short duration precipitation extremes are expected to increase under a warming climate at ≈7%K-1, following the Clausius-Claypeyron scaling relationship. Recent studies have analyzed global and regional scaling rates for precipitation extremes against temperature over an annual period, however assessment of seasonal variations of precipitation-temperature scaling, is largely unexplored, especially over the Indian subcontinent. Satellite derived and reanalysis based precipitation data sets can function as a suitable alternative to rain-gauge based data sets over data-sparse regions. In the present study, the performance of three high resolution data sets - GPM-IMERG satellite derived, ERA5 and IMDAA reanalysis precipitation - in determining the seasonal variations in precipitation-temperature scaling rates are investigated. When compared with the IMD data, IMERG and IMDAA capture the spatial variations and magnitude of scaling rates of daily precipitation extremes much better than ERA5. Two calibrated datasets - AIMERG and AERA5 are also analyzed and compared to IMD scaling rates. Following this, we further probe into the performance of the IMERG, ERA5 and IMDAA data sets over the entire Indian subcontinent, by including the results of scaling rates over oceans. The scaling rates of all three are found to be comparable in terms of magnitude and spatial distribution when analyzed over the entire Indian subcontinent. Significant seasonal variations in scaling rates are found over the Indian subcontinent, with the highest scaling rates in the post-monsoon and pre-monsoon seasons, and weaker rates in the monsoon season. Land–ocean contrast in scaling rates is evident across all seasons, but weak ocean scaling rates are found in the monsoon season for all three data sets.

Stormier Southern Hemisphere induced by topography and ocean circulation

A defining feature of Earth's present-day climate is that the Southern Hemisphere is stormier than the Northern Hemisphere. Consistently, the Southern Hemisphere has a stronger jet stream and more extreme weather events than the Northern Hemisphere. Understanding the relative importance of land-ocean contrast, including topography, radiative processes, and ocean circulation for determining this storminess asymmetry is important and may be helpful for interpreting projections of future storminess. Here, we show that the stormier Southern Hemisphere is induced by nearly equal contributions from topography and the ocean circulation, which moves energy from the Southern to Northern Hemisphere. These findings are based on 1) diagnostic energetic analyses applied to observations and climate model simulations and 2) modifying surface (land and ocean) boundary conditions in climate model simulations. Flattening topography and prescribing hemispherically symmetric surface energy fluxes (the manifestation of ocean energy transport on the atmosphere) in a climate model reduce the storminess asymmetry from 23 to 12% and 11%, respectively. Finally, we use the energetic perspective to interpret storminess trends since the beginning of the satellite era. We show that the Southern Hemisphere has become stormier, consistent with implied ocean energy transport changes in the Southern Ocean. In the Northern Hemisphere, storminess has not changed significantly consistent with oceanic and radiative (increased absorption of sunlight due to the loss of sea ice and snow) changes opposing one another. The trends are qualitatively consistent with climate model projections.

Multiple Environmental Influences on the Lightning of Cold-Based Continental Convection. Part II: Sensitivity Tests for Its Charge Structure and Land–Ocean Contrast

Abstract In Part I, an electrification scheme was described and a simulation of an observed cold-based storm from the U.S. Great Plains was validated with electrical observations. Most charge in the storm was separated by rebounding collisions of secondary ice originating from prior graupel–snow collisions. In this Part II, sensitivity tests are performed with the control simulation (Part I) and influences from environmental factors (aerosols, temperature, moisture, and shear) on lightning are elucidated. Environmental factors [e.g., convective available potential energy (CAPE)] controlling updraft speed are salient. When ascent is reduced by 30% and 70%, flashes become 70% fewer and disappear, respectively; faster ascent promotes positive cloud-to-ground (+CGs) flashes. Since cloud base is too cold (1°C) for coalescence, cloud condensation nucleus aerosol concentrations do not influence the lightning appreciably. The electrical response to varying concentrations of active ice nuclei is limited by most ice particles being secondary and less sensitive—a natural “buffer.” Imposing a maritime sounding suggests that the land–sea contrast in lightning for such storms is due to the vertical structure of environmental temperature and humidity. Weak CAPE, and both entrainment and condensate weight from a low cloud base, suppress ascent and charging. Maritime thermodynamic conditions reduce simulated flash rates by two orders of magnitude. Reducing aerosol loadings from continental to maritime only slightly reinforces this suppression. Last, a conceptual model is provided for how any simulated storm is either normal because graupel/hail is mostly positively charged or else is inverted/anomalous because graupel/hail is mostly negatively charged, with environmental factors controlling the charging. Impacts from microphysical processes, including three processes of secondary ice production, on lightning are analyzed.

Diurnal Cycle of Rainfall and Convective Properties over West and Central Africa

The need to investigate diurnal weather cycles in West Africa originates from the fact that complex interactions often result between mesoscale and synoptic weather processes. This study investigates diurnal cycles of rainfall and convective properties using six (6) hour interval data from the ERA-Interim and derived products from the Tropical Rainfall Measurement Mission (TRMM). Results showed that the land-ocean warming contrast is more strongly sensitive to the seasonal cycle, being very weak during March-May (MAM) but clearly spelled out during June-September (JJAS). Dipoles of wind convergence/divergence and wet/dry precipitation, between CASS and Nigeria Savannah zones, were identified in the morning and evening hours of MAM, whereas distinct night and day anomalies, same location in CASS, were found to be consistent during the JJAS season. The locations of flash count and system sizes agree with the climatology of convective properties, that morning and day-time hours are dominated by stratiform precipitation and small system sizes. Most results clearly showed that the eastern locations of Sudano and Sahel are consistently dry because rainfall and precipitation features are predominantly few. Very unique results about the dipole of wind and precipitation between two zones and the unusual dry zones of Sudan and Sahel have been found. Results presented had shown the importance of diurnal variation in understanding precipitation, flash count, system sizes patterns at diurnal scales, and understanding land-ocean contrast, precipitation and wind field anomaly at diurnal scales.

Vertical Characteristics of Raindrops Size Distribution over Sumatra Region from Global Precipitation Measurement Observation

The climatology of the vertical profile of raindrops size distribution (DSD) over Sumatra Region (10° S – 10° N, 90° E – 110° E) has been investigated using Global Precipitation Measurement (GPM) level 2 data from January 2015 to June 2018. DSD's vertical profile was observed through a vertical profile of corrected radar reflectivity (Ze) and two parameters of normalized gamma DSD, i.e., mass-weight mean diameter (Dm) and total drops concentration (Nw). Land-ocean contrast and rain type dependence of DSD over Sumatra were clearly observed. The values of Dm and Nw were larger in the land than in the ocean. Negative and positive gradients of Dm toward the surface were dominant during stratiform and convective rains, respectively, consistent with the Z gradient. Moreover, the negative gradient of stratiform rain in the ocean is larger than in land. Thus, the depletion of large drops is dominant over the ocean, which is due to the break-up process that can be observed from the increase of Nw. Raindrop growth of convective rains is more robust over the ocean than land that can be seen from a larger value of Dmgradient. The BB strength is slightly larger over land and coastal region than over the ocean, indicating that the riming process is more dominant over land and coastal regions than the ocean. Doi: 10.28991/esj-2021-01274 Full Text: PDF

Climatological sensitivities of shallow-cumulus bulk entrainment in continental and oceanic locations

AbstractCumulus entrainment is a complex process that has long challenged conceptual understanding and atmospheric prediction. To investigate this process observationally, two retrievals are used to generate multi-year climatologies of shallow-cumulus bulk entrainment (ϵ) at two Atmospheric Radiation Measurement cloud observatories, one in the US southern Great Plains (SGP) and the other in the Azores archipelago in the eastern North Atlantic (ENA). The statistical distributions of ϵ thus obtained, as well as certain environmental and cloud-related sensitivities of ϵ, are consistent with previous findings from large-eddy simulations. The retrieved ϵ robustly increases with cloudlayer relative humidity and decreases in wider clouds and cloud ensembles with larger cloud-base mass fluxes. While ϵ also correlates negatively with measures of cloud-layer vigor (e.g., maximum in-cloud vertical velocity and cloud depth), the extent to which these metrics actually regulate ϵ (or vice-versa) is unclear. Novel sensitivities of ϵ include a robust decrease of ϵ with increasing subcloud wind speed in oceanic flows, as well as a decrease of ϵ with increasing cloud-base mass flux in individual cumuli. A strong land–ocean contrast in ϵ is also found, with median values of 0.5-0.6 km−1 at the continental SGP site and and 1.0-1.1 km−1 at the oceanic ENA site. This trend is associated with drier and deeper cloud layers, along with larger cloud-base mass fluxes, at SGP, all of which favor reduced ϵ. The flow-dependence of retrieved ϵ implies that its various sensitivities should be accounted for in cumulus parameterization schemes.

Environmental sensitivities of shallow-cumulus dilution – Part 1: Selected thermodynamic conditions

Abstract. Cumulus entrainment, and its consequent dilution of buoyant cloud cores, strongly regulates the life cycle of shallow cumuli yet remains poorly understood. Herein, new insights into this problem are obtained through large-eddy simulations that systematically investigate the sensitivity of shallow-cumulus dilution to cloud-layer relative humidity (RH), cloud- and subcloud-layer depths, and continentality (i.e., the land–ocean contrast). The simulated cloud-core dilution is found to be strongly sensitive to continentality, with fractional dilution rates twice as large over the ocean as over land. Using a similarity theory based on the turbulent-kinetic-energy (TKE) budget, the reduced cloud-core dilution over land is attributed to larger cloud-base mass flux (mb), driven by stronger surface heating and subcloud turbulence. As mb increases, the fractional dilution rate must decrease to maintain energetic equilibrium. A positive sensitivity is also found to cloud-layer RH, with the core dilution increasing by 25 %–50 % for a 10 % enhancement in RH. This sensitivity is interpreted using the buoyancy-sorting hypothesis, in that mixtures of cloud and environmental air are more likely to become negatively buoyant and detrain (rather than diluting the cloud core) in drier cloud layers. By contrast, the sensitivities of (marine) shallow-cumulus dilution to cloud- and subcloud-layer depths are weak, with a 3 % decrease for a doubling for the former and a 4 % reduction in dilution for a 50 % deeper subcloud layer. These surprisingly weak sensitivities are readily explained by offsetting effects in the TKE similarity theory. Altogether, these experimental findings provide useful, though still incomplete, guidance for flow-dependent shallow-cumulus entrainment formulations in large-scale models.

Seasonality in power law scaling of convective and stratiform rainfall with lightning intensity over Indian Monsoon regions

The power law relationship between the rain (RT) and lightning flash (LF) is useful for estimating rainfall over poorly gauged catchment areas of rivers over north-east India (NEI) and that between LF and storm top height (STH) is key to lightning parametrization in models. However, they are poorly constrained over the Indian monsoon region where potential for significant changes exists with large spatial variability of rainfall, strong land-ocean contrast, seasonality and contribution of stratiform to total rainfall. Using 16 years of TRMM-PR data and LIS data, here we examine the RT and LF relationship and between LF and STH during pre-monsoon and monsoon seasons over four regions, NEI, Central India (CI), Bay of Bengal (BoB) and Indian Ocean (IO). A stronger power law (exponent b = 0.71) during pre-monsoon than that during the monsoon season (b = 0.58) apply for convective rain over land (including BoB) while a weaker relationship is applicable for stratiform rain with b = 0.60, and b = 0.47 respectively. Over IO, the relationship is nearly identical for convective and stratiform rain with no seasonality (b ~ 0.4). A power law poorly represents the LF-STH relationship over land and fails over IO. A fifth power law is applicable only for pre-monsoon convective rain over land weakening to half in monsoon seasons (b = 2.48). For stratiform rain it is weaker with (b = 3.27) and (b = 1.67) for pre-monsoon and monsoon seasons respectively. Our findings suggest that one threshold based lightning parameterizations are inadequate and need to be generalized to include regional and seasonal differences unraveled here.

Tropical rainfall subseasonal-to-seasonal predictability types

Tropical rainfall is mostly convective and its subseasonal-to-seasonal (S2S) prediction remains challenging. We show that state-of-art model forecast skill 3 + 4 weeks ahead is systematically lower over land than ocean, which is matched by a similar land-ocean contrast in the spatial scales of observed biweekly rainfall anomalies. Regional differences in predictability are then interpreted using observed characteristics of daily rainfall (wet-patch size, mean intensity as well as the strength of local S2S modes of rainfall variation), and classified into six S2S predictability types. Both forecast skill and spatial scales are reduced over the continents, either because daily rainfall patches are small and poorly organized by S2S modes of variation (as over equatorial and northern tropical Africa), or where the daily mean intensity is very high (as over South and SE Asia). Forecast skill and spatial scales are largest where daily rainfall is synchronized by intraseasonal (such as the Madden-Julian Oscillation) as well as interannual ocean-atmosphere modes of variation (such as El Niño-Southern Oscillation), especially over northern Australia and parts of the Maritime Continent, and over parts of eastern, southern Africa and northeast South America. The oceans exhibit the highest skill and largest spatial scales, especially where interannual (central equatorial Pacific) or intraseasonal (central and eastern Tropical Indian Ocean and Western Pacific) variability is largest. These results provide a relevant regional typology of the potential drivers and controls on S2S predictability of tropical rainfall, informing intrinsic limits and possible improvements toward useful S2S climate prediction at regional scale.

Boundary Layer Quasi-Equilibrium Limits Convective Intensity Enhancement from the Diurnal Cycle in Surface Heating

AbstractA combination of cloud-permitting model (CPM) simulations, satellite, and reanalysis data are used to test whether the diurnal cycle in surface temperature has a significant impact on the intensity of deep convection as measured by high-percentile updraft velocities, lightning, and CAPE. The land–ocean contrast in lightning activity shows that convective intensity varies between land and ocean independently from convective quantity. Thus, a mechanism that explains the land–ocean contrast must be able to do so even after controlling for precipitation variations. Motivated by the land–ocean contrast, we use idealized CPM simulations to test the impact of the diurnal cycle on high-percentile updrafts. In simulations, updrafts are somewhat enhanced due to large-scale precipitation enhancement by the diurnal cycle. To control for large-scale precipitation, we use statistical sampling techniques. After controlling for precipitation enhancement, the diurnal cycle does not affect convective intensities. To explain why sampled updrafts are not enhanced, we note that CAPE is also not increased, likely due to boundary layer quasi equilibrium (BLQE) occurring over our land area. Analysis of BLQE in terms of net positive and negative mass flux finds that boundary layer entrainment, and even more importantly downdrafts, account for most of the moist static energy (MSE) sink that is balancing surface fluxes. Using ERA-Interim data, we also find qualitative evidence for BLQE over land in the real world, as high percentiles of CAPE are not greater over land than over ocean.

Causes of future Mediterranean precipitation decline depend on the season

Future mean precipitation in the Mediterranean is projected to decrease year-round in response to global warming, threatening to aggravate water stress in the region, which can cause social and economic difficulties. We investigate possible causes of the Mediterranean drying in regional climate simulations. To test the influence of multiple large-scale drivers on the drying, we sequentially add them to the simulations. We find that the causes of the Mediterranean drying depend on the season. The summer drying results from the land-ocean warming contrast, and from lapse-rate and other thermodynamic changes, but only weakly depends on circulation changes. In contrast, to reproduce the simulated Mediterranean winter drying, additional changes in the circulation and atmospheric state have to be represented in the simulations. Since land-ocean contrast, thermodynamic and lapse-rate changes are more robust in climate simulations than circulation changes, the uncertainty associated with the projected drying should be considered smaller in summer than in winter.

Spatial and seasonal variability of clouds over the southwest Indian Ocean based on the DARDAR mask product

AbstractWe present a characterization of the variability of clouds over the southwest Indian Ocean between 2007 and 2010. Cloud occurrence is derived from the DARDAR (raDAR/liDAR) mask, a synergistic product based on Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat measurements. It provides a target classification for hydrometeors. We demonstrate that this product is suitable for studying the vertical, spatial and seasonal cloud distribution in the southwest Indian Ocean. The variability of cloud occurrence increases approaching the tropics: the average maximum amplitude of monthly occurrence is ∼7% between 30°S and 60°S and ∼14% between 10°S and 30°S. The 10–30°S latitudinal band exhibits the largest contrasts: summer (winter) total cloud occurrence is mainly driven by high‐ (low‐) level clouds. The vertical distribution of clouds differs on either side of 55°E and this is related to a land–ocean contrast and to large‐scale influence. In winter, east of 55°E, the maximum of cloud occurrence corresponds to warm and mixed‐phased precipitating clouds associated with the Mascarene High. In summer, west of 55°E, the vertical distribution of cloud occurrence is driven by deep convection associated with the InterTropical Convergence Zone and the Near Equatorial Trough. The vertical distribution of cloud occurrence shows an interannual variability that is related to El Niño events. The influence of other oscillation modes should be further investigated.

Land-sea contrasts for climatic lightning activity over Indian region

The land-ocean convective contrasts observed by the satellite-driven data from the Tropical Rainfall Measuring Mission for the year 1998 to 2014 (17 years) are analysed to examine the role of static land surface relative to the dynamic ocean surface for the lightning flash counts (FC). We present the relationship between the lightning flash counts per convective available potential energy (CAPE) (FC/CAPE), the product of CAPE and rainfall (CAPE × RF) and Bowen ratio, FC (land/ocean) and AOD (land/ocean) and FC (land/ocean) and maximum updraft speed (land/ocean) to examine the land-ocean contrasts over the Indian region. The results show that FC/CAPE over Indian land increases by up to 520% with respect to FC/CAPE over Indian oceanic regions. The land-ocean contrast seems to be a result of increase of Bowen ratio and FC over land by up to 800% as compared with Bowen ratio and FC over ocean surface. The increase of CAPE over land is by up to 47% relative to CAPE over ocean with corresponding increase of maximum updraft speed over land by up to 117% with respect to maximum updraft speed over ocean. The temperature profiles over the land and ocean show the same temperature in the lower troposphere, followed by a temperature difference of 8 °C between land and ocean at about 16000 m during pre-monsoon and post-monsoon periods. The product of CAPE with RF over land is higher by 66% to that of oceanic region with aerosol load (AOD) of about 49% more over land as compared with that of ocean. The results demonstrate the warming contrasts of land-ocean in a comparative analysis of FC, CAPE, RF and AOD in the tropics.

The climate effects of increasing ocean albedo: an idealized representation of solar geoengineering

Abstract. Geoengineering, or climate intervention, describes methods of deliberately altering the climate system to offset anthropogenic climate change. As an idealized representation of near-surface solar geoengineering over the ocean, such as marine cloud brightening, this paper discusses experiment G1ocean-albedo of the Geoengineering Model Intercomparison Project (GeoMIP), involving an abrupt quadrupling of the CO2 concentration and an instantaneous increase in ocean albedo to maintain approximate net top-of-atmosphere radiative flux balance. A total of 11 Earth system models are relatively consistent in their temperature, radiative flux, and hydrological cycle responses to this experiment. Due to the imposed forcing, air over the land surface warms by a model average of 1.14 K, while air over most of the ocean cools. Some parts of the near-surface air temperature over ocean warm due to heat transport from land to ocean. These changes generally resolve within a few years, indicating that changes in ocean heat content play at most a small role in the warming over the oceans. The hydrological cycle response is a general slowing down, with high heterogeneity in the response, particularly in the tropics. While idealized, these results have important implications for marine cloud brightening, or other methods of geoengineering involving spatially heterogeneous forcing, or other general forcings with a strong land–ocean contrast. It also reinforces previous findings that keeping top-of-atmosphere net radiative flux constant is not sufficient for preventing changes in global mean temperature.

The monsoon system: Land–sea breeze or the ITCZ?

For well over 300 years, the monsoon has been considered to be a gigantic land–sea breeze driven by the land–ocean contrast in surface temperature. In this paper, this hypothesis and its implications for the variability of the monsoon are discussed and it is shown that the observations of monsoon variability do not support this popular theory of the monsoon. An alternative hypothesis (whose origins can be traced to Blanford’s (1886) remarkably perceptive analysis) in which the basic system responsible for the Indian summer monsoon is considered to be the Intertropical Convergence Zone (ITCZ) or the equatorial trough, is then examined and shown to be consistent with the observations. The implications of considering the monsoon as a manifestation of the seasonal migration of the ITCZ for the variability of the Indian summer monsoon and for identification of the monsoonal regions of the world are briefly discussed.

Understanding Decreases in Land Relative Humidity with Global Warming: Conceptual Model and GCM Simulations

Abstract Climate models simulate a strong land–ocean contrast in the response of near-surface relative humidity to global warming; relative humidity tends to increase slightly over oceans but decrease substantially over land. Surface energy balance arguments have been used to understand the response over ocean but are difficult to apply over more complex land surfaces. Here, a conceptual box model is introduced, involving atmospheric moisture transport between the land and ocean and surface evapotranspiration, to investigate the decreases in land relative humidity as the climate warms. The box model is applied to simulations with idealized and full-complexity (CMIP5) general circulation models, and it is found to capture many of the features of the simulated changes in land humidity. The simplest version of the box model gives equal fractional increases in specific humidity over land and ocean. This relationship implies a decrease in land relative humidity given the greater warming over land than ocean and modest changes in ocean relative humidity, consistent with a mechanism proposed previously. When evapotranspiration is included, it is found to be of secondary importance compared to ocean moisture transport for the increase in land specific humidity, but it plays an important role for the decrease in land relative humidity. For the case of a moisture forcing over land, such as from stomatal closure, the response of land relative humidity is strongly amplified by the induced change in land surface–air temperature, and this amplification is quantified using a theory for the link between land and ocean temperatures.

Separating climate change signals into thermodynamic, lapse-rate and circulation effects: theory and application to the European summer climate

Climate models robustly project a strong overall summer warming across Europe showing a characteristic north-south gradient with enhanced warming and drying in southern Europe. However, the processes that are responsible for this pattern are not fully understood. We here employ an extended surrogate or pseudo-warming approach to disentangle the contribution of different mechanisms to this response pattern. The basic idea of the surrogate technique is to use a regional climate model and apply a large-scale warming to the lateral boundary conditions of a present-day reference simulation, while maintaining the relative humidity (and thus implicitly increasing the specific moisture content). In comparison to previous studies, our approach includes two important extensions: first, different vertical warming profiles are applied in order to separate the effects of a mean warming from lapse-rate effects. Second, a twin-design is used, in which the climate change signals are not only added to present-day conditions, but also subtracted from a scenario experiment. We demonstrate that these extensions provide an elegant way to separate the full climate change signal into contributions from large-scale thermodynamic (TD), lapse-rate (LR), and circulation and other remaining effects (CO). The latter in particular include changes in land-ocean contrast and spatial variations of the SST warming patterns. We find that the TD effect yields a large-scale warming across Europe with no distinct latitudinal gradient. The LR effect, which is quantified for the first time in our study, leads to a stronger warming and some drying in southern Europe. It explains about 50 % of the warming amplification over the Iberian Peninsula, thus demonstrating the important role of lapse-rate changes. The effect is linked to an extending Hadley circulation. The CO effect as inherited from the driving GCM is shown to further amplify the north-south temperature change gradient. In terms of mean summer precipitation the TD effect leads to a significant overall increase in precipitation all across Europe, which is compensated and regionally reversed by the LR and CO effects in particular in southern Europe.

"On the Land-Ocean Contrast of Tropical Convection and Microphysics Statistics Derived from TRMM Satellite Signals and Global Storm-Resolving Models".

A 14-year climatology of Tropical Rainfall Measuring Mission (TRMM) collocated multi-sensor signal statistics reveal a distinct land-ocean contrast as well as geographical variability of precipitation type, intensity, and microphysics. Microphysics information inferred from the TRMM precipitation radar and Microwave Imager (TMI) show a large land-ocean contrast for the deep category, suggesting continental convective vigor. Over land, TRMM shows higher echo-top heights and larger maximum echoes, suggesting taller storms and more intense precipitation, as well as larger microwave scattering, suggesting the presence of more/larger frozen convective hydrometeors. This strong land-ocean contrast in deep convection is invariant over seasonal and multi-year time-scales. Consequently, relatively short-term simulations from two global storm-resolving models can be evaluated in terms of their land-ocean statistics using the TRMM Triple-sensor Three-step Evaluation via a satellite simulator. The models evaluated are the NASA Multi-scale Modeling Framework (MMF) and the Non-hydrostatic Icosahedral Cloud Atmospheric Model (NICAM). While both simulations can represent convective land-ocean contrasts in warm precipitation to some extent, near-surface conditions over land are relatively moisture in NICAM than MMF, which appears to be the key driver in the divergent warm precipitation results between the two models. Both the MMF and NICAM produced similar frequencies of large CAPE between land and ocean. The dry MMF boundary layer enhanced microwave scattering signals over land, but only NICAM had an enhanced deep convection frequency over land. Neither model could reproduce a realistic land-ocean contrast in in deep convective precipitation microphysics. A realistic contrast between land and ocean remains an issue in global storm-resolving modeling.

전지구 온도지표를 이용한 한강유역의 여름철 몬순 강우예측의 적용성 평가

본 연구에서는 LOC/MTG 온도지표를 이용하여 한강유역의 강우변동특성을 분석하였다. 장기간의 온도인자에 내포되어 있는 비정상 진동의 복합적인 특성을 파악하기 위해 EEMD(Ensemble Empirical Mode Decomposition) 기법을 적용하여 유한개의 진동패턴인 IMFs(Intrinsic mode functions)를 추출하였으며, MLP-ANN(Multi-layer Perceptron Artificial Neural Network) 기법을 적용하여 두 온도지표의 단기예측을 실시하였다. 또한 트리모델을 통하여 두 온도지표에 따른 여름철 강우 및 비태풍 강우에 대한 그룹화를 실시하여 한강유역의 장래 강우 발생에 대한 예측의 적용가능성을 검토하였다. In the current study, we analyzed the characteristics of summer precipitation variability in the Han River basin using the Land-Ocean Contrast (LOC) and Meridional Temperature Gradient (MTG) temperature indices. To analyze the complex characteristics of abnormal variations internalized in the long-term temperature indices, the Ensemble Empirical Mode Decomposition (EEMD) method was applied to extract Intrinsic Mode Functions (IMFs), a finite number of variation patterns. The extended IMFs were applied to the Multi-layer Perceptron Artificial Neural Network (MLP-ANN) model to forecast the short-term period of two temperature indices. In addition, we performed grouping on summer precipitation with using decision making model, Tree model. We also, studied nontyphoons precipitation in consideration of the complex effects of the two temperature indices and examined the applicability of forecast regarding the monsoon related precipitation during the summer season over the Han River basin.