Atmospheric Transfer Research Articles

Polarized radiative transfer in planetary atmospheres and the polarization of exoplanets

We describe the incorporation of polarized radiative transfer into the atmospheric radiative transfer modelling code VSTAR (Versatile Software for Transfer of Atmospheric Radiation). Using a vector discrete-ordinate radiative transfer code we are able to generate maps of radiance and polarization across the disc of a planet, and integrate over these to get the full-disc polarization. In this way we are able to obtain disc-resolved, phase-resolved and spectrally-resolved intensity and polarization for any of the wide range of atmopsheres that can be modelled with VSTAR. We have tested the code by reproducing a standard benchmark problem, as well as by comparing with classic calculations of the polarization phase curves of Venus. We apply the code to modelling the polarization phase curves of the hot Jupiter system HD 189733b. We find that the highest polarization amplitudes are produced with optically thick Rayleigh scattering clouds and these would result in a polarization amplitude of 27 ppm for the planetary signal seen in the combined light of the star and planet. A more realistic cloud model consistent with the observed transmission spectrum results is an amplitude of ~20 ppm. Decreasing the optical depth of the cloud, or making the cloud particles more absorbing, both have the effect of increasing the polarization of the reflected light but reducing the amount of reflected light and hence the observed polarization amplitude.

MERCURY CONTENT LEVELS IN HAIR OF RURAL POPULATION OF THE YAMAL-NENETS AUTONOMOUS DISTRICT

Mercury is capable of atmospheric transfer by large distances, offers resistance to the environment, is able to bioaccumulation in ecosystems and leads to significant negative consequences for the public health. Aim: to study the mercury content in the hair of rural residents of the Yamalo-Nenets Autonomous District and assess the population health risks. Methods: A single-step epidemiological study was conducted with the formation of a representative selection of rural residents in the Yamal-Nenets Autonomous District. The hair samples were taken from the occipital part of the head using a standard WHO technique. Chemicoanalytical study of samples wwas carried out in a licensed laboratory using mass-spectrographic method with inductively coupled argon plasma. The statistical analysis was performed using the Statistica v.8.0 program. Differences were assessed as statistically significant at p < 0.05. Results: Mercury concentration in the hair of the inhabitants living in the rural settlements varied from 0.204gg/g to 9.99 gg/g and those leading the traditional (nomadic) lifestyle varied from 0.303 gg/g to 5.21 gg/g. Increased risk to public health of Tazovsky settlement was detected in 48.8 % of cases, for residents who led the traditional way of life in Gydansky, Antipayutinskaya and Nakhodka tundra - 86.6 %, Harsaim settlement - 77.3 %. Absolute average values of mercury content in hair of the aboriginal population were 2.6 times higher than in the migrants. Conclusions: It is necessary to strengthen control over mercury content in natural environments and its accumulation in food chains and to carry out measures to reduce the population health risk.

Exploring Accommodation Cluster and Tourism Development Based on GPS Positioning and GIS Analysis

This research aims to locate a set of points of B&B accommodations on a coffee cultivation area by using GPS positioning and GIS spatial analysis for responding to Porter's concept of industry cluster and to analyze the locational factors of B&B accommodation. Due to the coffee attractiveness, the B&B lodging establishments have sprung up in the area like mushrooms to service more and more tourists for the past 20 years. The spatial cluster of B&B establishments is displayed by specifying a set of GPS positioning points on different GIS raster surfaces to process point density analysis, buffer analysis and terrain analysis. To explore the locational characteristic of B&B establishments, overlay analysis is processed to examine the terrain, landscape, accessibility and tourist attractiveness factors. Instead of focusing on innovation atmosphere, knowledge intensive and technology transfer of new industry cluster factors, this research emphasizes traditional cluster concept of geography proximity on the benefits of agriculture and tourism linkage to available of tourist foods.

Evaluation of TOPMODEL-Based Land Surface–Atmosphere Transfer Scheme (TOPLATS) through a Soil Moisture Simulation

Abstract Better quantification of the spatiotemporal distribution of soil moisture across different spatial scales contributes significantly to the understanding of land surface processes on the Earth as an integrated system. While observational data for root-zone soil moisture (RZSM) often have sparse spatial coverage, model-simulated soil moisture may provide a useful alternative. TOPMODEL-Based Land Surface–Atmosphere Transfer Scheme (TOPLATS) has been widely studied and actively modified in recent years, while a detailed regional application with evaluation currently is still lacking. Thus, TOPLATS was used to generate high-resolution (30 arc s) RZSM based on coarse-scale (0.125°) forcing data over part of the Arkansas–Red River basin. First, the simulated RZSM was resampled to coarse scale to compare with the results of Mosaic, Noah, and VIC from NLDAS. Second, TOPLATS performance was assessed based on the spatial absolute difference among the models. The comparison shows that TOPLATS performance is similar to VIC, but different from Mosaic and Noah. Last, the simulated RZSM was compared with in situ observations of 16 stations in the study area. The results suggest that the simulated spatial distribution of RZSM is largely consistent with the distribution of topographic index (TI) in most instances, as topography was traditionally considered a major, but not the only, factor in horizontal redistribution of soil moisture. In addition, the finer-resolution RZSM can reflect the in situ soil moisture change at most local sites to a certain degree. The evaluation confirms that TOPLATS is a useful tool to estimate high-resolution soil moisture and has great potential to provide regional soil moisture estimates.

Air-Seawater Gas Exchange and Dry Deposition of Chlorinated Paraffins in a Typical Inner Sea (Liaodong Bay), North China.

As a group of new persistent organic pollutants, short-chain chlorinated paraffins (SCCPs) and medium-chain CP (MCCPs) have attracted extensive worldwide interest in recent years. However, the data regarding to the environmental behavior, especially in atmospheric transfer and air-seawater exchange, are still sparse. In this study, seasonal marine boundary layer air and seawater samples were collected from Chinese Bohai sea and a fugacity model was built to evaluate the air-seawater diffusion and deposition flux of CPs. Generally, the total CP levels in atmosphere and seawater samples in summer were higher than those in spring, and CPs existed mostly in the gaseous phase in air and the dissolved phase in seawater. For SCCPs, C10 and C11 components were the most abundant homologue groups. For MCCPs, the C14 homologue dominated in the particle phase of atmosphere and particulate phase of seawater. The logarithmic fugacity ratios (log fa/ fw) of higher chlorinated congeners (Cl8 to Cl10: 0.71 to 1.32 in May and 1.38 to 2.29 in August) indicated that net deposition was the predominant process, whereas lower chlorinated congeners, especially Cl5 homologue groups in August, showed a trend of net volitization (log fa/ fw < -0.5). The results of diffusion and dry deposition fluxes indicated that air-seawater gas exchange of CPs was significantly higher than dry deposition in the sampling areas.

Laser-based atmospheric radio-frequency transfer with sub-picosecond timing fluctuation using single phase compensator

We demonstrate a 100-m long outdoor laser-based atmospheric transfer with sub-picosecond timing fluctuation using a single phase compensator setup. With this frequency transfer scheme, a 1 GHz radio-frequency signal has been transferred over a 100 m atmospheric link. Timing fluctuation and instability were measured to evaluate the quality of the distributed frequency signal. The experimental results show the root-mean-square timing fluctuation of the transferred frequency signal is 441 fs within 5000 s, with a relative fractional frequency instability of 2 × 10−13 @ 1 s and 2 × 10−16 @ 1000 s. The proposed frequency transfer technique with single phase compensator has a potential application that disseminating a commercial Cs clock and H-master signal in free space since the stability of the transmission link is superior to these atomic clocks.

Evaluation of a new inference method for estimating ammonia volatilisation from multiple agronomic plots

Abstract. Tropospheric ammonia (NH3) is a threat to the environment and human health and is mainly emitted by agriculture. Ammonia volatilisation following application of nitrogen in the field accounts for more than 40 % of the total NH3 emissions in France. This represents a major loss of nitrogen use efficiency which needs to be reduced by appropriate agricultural practices. In this study we evaluate a novel method to infer NH3 volatilisation from small agronomic plots consisting of multiple treatments with repetition. The method is based on the combination of a set of NH3 diffusion sensors exposed for durations of 3 h to 1 week and a short-range atmospheric dispersion model, used to retrieve the emissions from each plot. The method is evaluated by mimicking NH3 emissions from an ensemble of nine plots with a resistance analogue–compensation point–surface exchange scheme over a yearly meteorological database separated into 28-day periods. A multifactorial simulation scheme is used to test the effects of sensor numbers and heights, plot dimensions, source strengths, and background concentrations on the quality of the inference method. We further demonstrate by theoretical considerations in the case of an isolated plot that inferring emissions with diffusion sensors integrating over daily periods will always lead to underestimations due to correlations between emissions and atmospheric transfer. We evaluated these underestimations as −8 % ± 6 % of the emissions for a typical western European climate. For multiple plots, we find that this method would lead to median underestimations of −16 % with an interquartile [−8–22 %] for two treatments differing by a factor of up to 20 and a control treatment with no emissions. We further evaluate the methodology for varying background concentrations and NH3 emissions patterns and demonstrate the low sensitivity of the method to these factors. The method was also tested in a real case and proved to provide sound evaluations of NH3 losses from surface applied and incorporated slurry. We hence showed that this novel method should be robust and suitable for estimating NH3 emissions from agronomic plots. We believe that the method could be further improved by using Bayesian inference and inferring surface concentrations rather than surface fluxes. Validating against controlled source is also a remaining challenge.

Discrete spherical harmonics method for radiative transfer in scalar planar inhomogeneous atmosphere.

The radiative transfer problems in a participating inhomogeneous scalar planar atmosphere, subjected to diffuse or collimated incidence, are investigated using the discrete spherical harmonics method. In developing the method, the radiative intensity is expanded in a finite series of Legendre polynomials and the resulting first-order coupled differential equations of radiance moments are expressed in a set of discrete polar directions. The method is applied to homogeneous/inhomogeneous atmospheres of various anisotropic scattering degrees and thicknesses, and reflective boundary conditions. The discrete spherical harmonics method albedo, transmittance, and radiative intensity predictions agree well with benchmark literature results. Additionally, numerical predictions show that the discrete spherical harmonics method using Mark boundary conditions are more efficient than using Marshak boundary conditions.

Spatial differences in the accumulation of elements by the lichen Cladonia rangiferina L. in the Pasvik Nature Reserve

Nature Reserve and its surroundings (the Murmansk Region). The most significant factor influencing the accumulation of elements is the distance to non-ferrous metal industry facilities (industrial sites of the Kola Mining and Metallurgic Company (Kola MMC) of the Norilsk Nickel Holding). The exponential function proved to be well fit for this dependence. The elements fall into two groups: 1) elements present in the plant’s emissions and having a pronounced spatial gradient in the nature reserve and its surroundings (Cr, Fe, Co, Cu, Ni, Cd, Pb, As), and 2) elements which have no clear patterns in the distribution and depend on the “background” values (Zn, Mn and Hg). The concentrations of group 1 pollutants in the lichen decreased at a rate of 2–5 % for each kilometer of distance from the source of emissions. The content of most of the elements significantly (p &lt; 0.05) correlated with each other. The exception was Mn, whose content was inhibited by an increase in the concentrations of other metals (primarily Pb, Fe, Co). Even samples with the lowest Ni, Cu, Co and Cd content from the sites furthest away from the source in the Pasvik Reserve and its surroundings had the elements concentrations higher than the environmental ‘background’ for adjacent tundra communities (Kanin tundra, Nenets Autonomous District). Lichens of the Pasvik Reserve accumulate higher concentrations of the main pollutants (Ni, Cu, Co and Fe) than vascular plants in the same territory. Graphic isopleths of the distribution of potential contaminant concentrations in lichen thalli were plotted for the territory of the reserve. The Pasvik Nature Reserve was used as the example to demonstrate that, at present, ecosystem components within protected areas cannot be regarded as geochemical standards for the regional environment due the regional atmospheric transfers from nearby industrial facilities.

Thallium contamination of desert soil in Namibia: Chemical, mineralogical and isotopic insights

We studied arid desert soils from Namibia (Rosh Pinah) that were contaminated with up to 7 mg kg−1 of thallium (Tl) via dust emitted from a local flotation tailing dam. Chemical extractions of waste and soil materials indicated that most of the Tl is strongly bound, in accordance with X-ray diffraction and X-ray absorption spectroscopy data that point to the predominant association of Tl with metal sulfides and phyllosilicates. The isotope fractionation factor ε205Tl of the soil samples (from −0.4 to +3.8) shows a positive linear relationship (R2 = 0.62) with 1/Tl, indicative for the mixing of two major Tl pools, presumably anthropogenic Tl and geogenic Tl. The ε205Tl value for the topmost soil samples (∼+3) closely matches the ε205Tl value for post-flotation waste particles with a diameter of <0.05 mm, whereas the bulk flotation waste exhibits a significantly larger ε205Tl value (∼+6). These variations are in accordance with predominant atmospheric transfer of Tl from the tailings to the adjacent soils via fine (dust) particles. The identified minimal Tl alteration in soils indicates that only a small part of the Tl could be potentially released and passively enter the vegetation, local population and/or food chain in the long term. From this viewpoint, Tl does not represent such an important environmental concern as other (abundant) contaminants at the locality. Furthermore, there could be a relevance for other alkaline desert soils, including those where Tl pollution plays a major role.

GaAs/Ge/GaAs Heterostructures for Use in Nonlinear Optics

GaAs/Ge/GaAs heterostructures with sublattice reversed GaAs on Ge epilayers grown via molecular beam epitaxy (MBE) for periodic domain inverted structures are presented. For the first time, such structures are grown in separate MBE machines for GaAs and Ge with atmospheric wafer transfer. The high quality of the heterostructures is confirmed via X-ray diffraction and photoluminescence. It is proposed that the surfactants (Bi, Sb) be used to control the nucleation of GaAs epilayers on a Ge epilayer.

Low genetic variation between South American and Antarctic populations of the bank-forming moss Chorisodontium aciphyllum (Dicranaceae)

The Antarctic–South American bank-forming moss Chorisodontium aciphyllum is known for having the oldest sub-fossils of any extant plant in Antarctica as well as extreme survival abilities, making it a candidate species for possible long-term survival in Antarctica. Applying phylogeographic and population genetic methods using the plastid markers trnL-F and rps4 and the nuclear internal transcribed spacer, we investigated the genetic diversity within C. aciphyllum throughout its range. Low genetic variation was found in all loci, both between and within Antarctic and southern South American populations, suggesting a relatively recent (likely within the last million years) colonization of this moss to the Antarctic, as well as a likely severe bottleneck during Pleistocene glaciations in southern South America. We also performed a simple atmospheric transfer modeling approach to study potential colonization rates of small (microscopic/microbial) or spore-dispersed organisms (such as many mosses and lichens). These suggested that the northern Antarctic Peninsula shows potentially regular connectivity from southern South America, with air masses transferring, particularly southbound, between the two regions. We found elevated genetic variation of C. aciphyllum in Elephant Island, also the location of the oldest known moss banks (> 5500 years), suggesting this location to be a genetic hotspot for this species in the Antarctic.

Tree-, stand- and site-specific controls on landscape-scale patterns of transpiration

Abstract. Transpiration is a key process in the hydrological cycle, and a sound understanding and quantification of transpiration and its spatial variability is essential for management decisions as well as for improving the parameterisation and evaluation of hydrological and soil–vegetation–atmosphere transfer models. For individual trees, transpiration is commonly estimated by measuring sap flow. Besides evaporative demand and water availability, tree-specific characteristics such as species, size or social status control sap flow amounts of individual trees. Within forest stands, properties such as species composition, basal area or stand density additionally affect sap flow, for example via competition mechanisms. Finally, sap flow patterns might also be influenced by landscape-scale characteristics such as geology and soils, slope position or aspect because they affect water and energy availability; however, little is known about the dynamic interplay of these controls. We studied the relative importance of various tree-, stand- and site-specific characteristics with multiple linear regression models to explain the variability of sap velocity measurements in 61 beech and oak trees, located at 24 sites across a 290 km2 catchment in Luxembourg. For each of 132 consecutive days of the growing season of 2014 we modelled the daily sap velocity and derived sap flow patterns of these 61 trees, and we determined the importance of the different controls. Results indicate that a combination of mainly tree- and site-specific factors controls sap velocity patterns in the landscape, namely tree species, tree diameter, geology and aspect. For sap flow we included only the stand- and site-specific predictors in the models to ensure variable independence. Of those, geology and aspect were most important. Compared to these predictors, spatial variability of atmospheric demand and soil moisture explains only a small fraction of the variability in the daily datasets. However, the temporal dynamics of the explanatory power of the tree-specific characteristics, especially species, are correlated to the temporal dynamics of potential evaporation. We conclude that transpiration estimates on the landscape scale would benefit from not only consideration of hydro-meteorological drivers, but also tree, stand and site characteristics in order to improve the spatial and temporal representation of transpiration for hydrological and soil–vegetation–atmosphere transfer models.

Cryospheric Hydrometeorology Observation in the Hulu Catchment (CHOICE), Qilian Mountains, China

Core Ideas CHOICE is an observation platform for field, hillside, catchment and mountainous basin scales. A distributed hydrological model including cryospheric hydrology data is needed. CHOICE is an open cryospheric hydrology observation and research system. Understanding cryospheric hydrology and the effects of cryospheric changes on river runoff is critical for sustainable water management especially in arid inland river basins such as those in northwest China where water resources mainly come from alpine areas. A cryospheric hydrometeorology observation system (CHOICE) has been established since 2008 in the Hulu catchment, which is a well‐instrumented experimental and representative catchment in the upper reaches of the inland Hei River, Qilian Mountains, northwest China. The CHOICE includes dense meteorological measurements from 2980 to 4800 m asl (e.g. glacier, snow, and permafrost hydrology) and water and heat balance in the vertical landscape zones including alpine grassland, meadow, shrub, coniferous forest, marshy meadow, and moraine‐talus zones. The comprehensive long‐term observations available for the CHOICE provide the basis for model development and application in cryospheric hydrological research. We focus on cryospheric hydrometeorological process of precipitation, freeze–thaw cycle, energy balance, soil–vegetation–atmosphere transfer (SVAT), runoff, groundwater reservoir, and hydrological resiliency within vertical elevation in CHIOCE. Data from CHOICE, an open cryospheric hydrology observation and research system, is accessed through a website (http://hhsy.casnw.net/) and the WestDC database (http://westdc.westgis.ac.cn/).

A Unified Formulation of Radiative Transfer in Plane-Parallel Atmospheres Based on General Decomposition of Radiance. Part II: An Exemplifying Application to the Hemispherical Harmonics Method with Four Components

Abstract Based on the unified formulation, the so-called hemispherical harmonics method with four components (HSHM4) is derived following the general procedure described in the first paper of this series. The numerical results of this method, including the flux reflections, transmissions, and absorptions for different optical depths, incident beam angles, and single-scattering albedos and the emissions for different optical depths and single-scattering albedos, are reported, in comparison with the results of DISORT with 128 streams as a benchmark. The application of the method to the radiation scheme for climate models is illustrated with the numerical results, including the heating-rate profiles for the shortwave and longwave radiation, radiative fluxes at the top and the bottom boundaries of the atmosphere, and the actinic flux profiles, for typical model atmospheres of Earth and different clear or cloudy conditions. The comparison of results with those of the discrete ordinate methods (DOMs) and the spherical harmonic method (SHM) with four components shows that the HSHM4 has comparable accuracy with the four-stream DOM with double-Gaussian quadrature and is more accurate than the four-stream SHM and the four-stream DOM with full-range Gaussian quadrature in general, especially in the cases of longwave radiation when the multiple-scattering effect should be accounted for. The HSHM4 can be deployed consistently to all of the bands without artificial division between the longwave and shortwave. The development and validation of the HSHM4 exhibit the usefulness of the unified formulation in the study of atmospheric radiative transfer.

A Unified Formulation of Radiative Transfer in Plane-Parallel Atmospheres Based on General Decomposition of Radiance. Part I: The Theory

Abstract A unified formulation of the general decomposition of radiance and the radiative transfer equation (RTE) of plane-parallel atmospheres and the general solutions of the generally decomposed RTE system (GD-RTES) are presented. It is shown that the eigenvalues of the coefficient matrix of the GD-RTES are real and the eigenvectors are independent of each other when the single-scattering albedo is less than unity; the general solution of the GD-RTES for a homogeneous layer can then be expressed in combinations of the exponential functions of the optical depth. The solution for nonhomogeneous atmosphere–surface systems can be obtained through either the matrix operator method or the linear system method. An outline of the general procedure is given, and a detailed example will be provided in Part II of this work. The formulation can serve as a meta-algorithm from which the prototypes of new algorithms can be developed and tested. Some of the conventional methods such as the discrete ordinate method and the spherical harmonic method can be considered as instances of the unified formulation. With the unified formulation, some interesting topics about the RTE and its solution can be discussed more generally, such as those about correction for energy conservation, treatment of boundary conditions, and transformation for numerical stability; some of the methods that have already proved useful to these issues in the well-established algorithms can be generalized to be available to the other methods that can be derived from the unified formulation.

Rapid atmospheric transport and large-scale deposition of recently synthesized plant waxes

Sedimentary plant wax 2H/1H ratios are important tools for understanding hydroclimate and environmental changes, but large spatial and temporal uncertainties exist about transport mechanisms from ecosystem to sediments. To assess atmospheric pathways, we collected aerosol samples for two years at four locations within a ∼60 km radius in northern Switzerland. We measured n-alkane distributions and 2H/1H ratios in these samples, and from local plants, leaf litter, and soil, as well as surface sediment from six nearby lakes. Increased concentrations and 2H depletion of long odd chain n-alkanes in early summer aerosols indicate that most wax aerosol production occurred shortly after leaf unfolding, when plants synthesize waxes in large quantities. During autumn and winter, aerosols were characterized by degraded n-alkanes lacking chain length preferences diagnostic of recent biosynthesis, and 2H/1H values that were in some cases more than 100‰ higher than growing season values. Despite these seasonal shifts, modeled deposition-weighted average 2H/1H values of long odd chain n-alkanes primarily reflected summer values. This was corroborated by n-alkane 2H/1H values in lake sediments, which were similar to deposition-weighted aerosol values at five of six sites. Atmospheric deposition rates for plant n-alkanes on land were ∼20% of accumulation rates in lakes, suggesting a role for direct deposition to lakes or coastal oceans near similar production sources, and likely a larger role for deposition on land and transport in river systems. This mechanism allows mobilization and transport of large quantities of recently produced waxes as fine-grained material to low energy sedimentation sites over short timescales, even in areas with limited topography. Widespread atmospheric transfer well before leaf senescence also highlights the importance of the isotopic composition of early season source water used to synthesize waxes for the geologic record.

Influence of speckle image reconstruction on photometric precision for large solar telescopes

Context. High-resolution observations from large solar telescopes require adaptive optics (AO) systems to overcome image degradation caused by Earth’s turbulent atmosphere. AO corrections are, however, only partial. Achieving near-diffraction limited resolution over a large field of view typically requires post-facto image reconstruction techniques to reconstruct the source image.Aims. This study aims to examine the expected photometric precision of amplitude reconstructed solar images calibrated using models for the on-axis speckle transfer functions and input parameters derived from AO control data. We perform a sensitivity analysis of the photometric precision under variations in the model input parameters for high-resolution solar images consistent with four-meter class solar telescopes.Methods. Using simulations of both atmospheric turbulence and partial compensation by an AO system, we computed the speckle transfer function under variations in the input parameters. We then convolved high-resolution numerical simulations of the solar photosphere with the simulated atmospheric transfer function, and subsequently deconvolved them with the model speckle transfer function to obtain a reconstructed image. To compute the resulting photometric precision, we compared the intensity of the original image with the reconstructed image.Results. The analysis demonstrates that high photometric precision can be obtained for speckle amplitude reconstruction using speckle transfer function models combined with AO-derived input parameters. Additionally, it shows that the reconstruction is most sensitive to the input parameter that characterizes the atmospheric distortion, and sub-2% photometric precision is readily obtained when it is well estimated.

Soil temperature response in Korea to a changing climate using a land surface model

The land surface processes play an important role in weather and climate systems through its regulation of radiation, heat, water and momentum fluxes. Soil temperature (ST) is one of the most important parameters in the land surface processes; however, there are few extensive measurements of ST with a long time series in the world. According to the CLImatology of Parameters at the Surface (CLIPS) methodology, the output of a trusted Soil-Vegetation- Atmosphere Transfer (SVAT) scheme can be utilized instead of observations to investigate the regional climate of interest. In this study, ST in South Korea is estimated in a view of future climate using the output from a trusted SVAT scheme — the University of TOrino model of land Process Interaction with Atmosphere (UTOPIA), which is driven by a regional climate model. Here characteristic changes in ST are analyzed under the IPCC A2 future climate for 2046-2055 and 2091-2100, and are compared with those under the reference climate for 1996-2005. The UTOPIA results were validated using the observed ST in the reference climate, and the model proved to produce reasonable ST in South Korea. The UTOPIA simulations indicate that ST increases due to environmental change, especially in air temperature (AT), in the future climate. The increment of ST is proportional to that of AT except for winter. In wintertime, the ST variations are different from region to region mainly due to variations in snow cover, which keeps ST from significant changes by the climate change.

Coupling of Community Land Model with RegCM4 for Indian Summer Monsoon Simulation

Three land surface schemes available in the regional climate model RegCM4 have been examined to understand the coupling between land and atmosphere for simulation of the Indian summer monsoon rainfall. The RegCM4 is coupled with biosphere–atmosphere transfer scheme (BATS) and the National Center for Atmospheric Research (NCAR) Community Land Model versions 3.5, and 4.5 (CLM3.5 and CLM4.5, respectively) and model performance is evaluated for recent drought (2009) and normal (2011) monsoon years. The CLM4.5 has a more distinct category of surface and it is capable of representing better the land surface characteristics. National Centers for Environmental Prediction (NCEP) and Department of Energy (DOE) reanalysis version 2 (NNRP2) datasets are considered as driving force to conduct the experiments for the Indian monsoon region (30°E–120°E; 30°S–50°N). The NNRP2 and India Meteorological Department (IMD) gridded precipitation data are used for verification analysis. The results indicate that RegCM4 simulations with CLM4.5 (RegCM4–CLM4.5) and CLM3.5 (RegCM4–CLM3.5) surface temperature (at 2 ms) have very low warm biases (~1 °C), while with BATS (RegCM4–BATS) has a cold bias of about 1–3 °C in peninsular India and some parts of central India. Warm bias in the RegCM4–BATS is observed over the Indo-Gangetic plain and northwest India and the bias is more for the deficit year as compared to the normal year. However, the warm (cold) bias is less in RegCM4–CLM4.5 than other schemes for both the deficit and normal years. The model-simulated maximum (minimum) surface temperature and sensible heat flux at the surface are positively (negatively) biased in all the schemes; however, the bias is higher in RegCM4–BATS and lower in RegCM4–CLM4.5 over India. All the land surface schemes overestimated the precipitation in peninsular India and underestimated in central parts of India for both the years; however, the biases are less in RegCM4–CLM4.5 and more in RegCM4–CLM3.5 and RegCM4–BATS. During both the years, BATS scheme in RegCM4 failed to represent low precipitation over the leeward than windward side of the Western Ghats, while CLM schemes (both versions) in the RegCM4 are able to depict this feature. In the topographic regions, such as the Western Ghats, northeast India and state of Jammu and Kashmir, RegCM4–BATS overestimates the rainfall amount with higher bias. Statistical analysis using anomaly correlation coefficient, root mean square error, equitable threat score, and critical success index confirms that RegCM4–CLM performs better than RegCM4–BATS in the simulation of the Indian summer monsoon.