Isothermal diffusion of water vapor in unsaturated soils based on Fick’s second law

In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.

REMOTE SENSING OF WATER VAPOR CONTENT USING GROUND-BASED GPS DATA

Spatial and temporal resolution of water vapor content is useful in improving the accuracy of short_term weather prediction.Dense and continuously tracking regional GPS arrays will play an important role in remote sensing atmospheric water vapor content.In this study,a piecewise linear solution method was proposed to estimate the precipitable water vapor (PWV) content from ground_based GPS observations in Hong Kong.To evaluate the solution accuracy of the water vapor content sensed by GPS,the upper air sounding data (radiosonde) that are collected locally was used to calculate the precipitable water vapor during the same period.One_month results of PWV from both ground_based GPS sensing technique and radiosonde method are in agreement within 1～2 mm.This encouraging result will motivate the GPS meteorology application based on the establishment of a dense GPS array in Hong Kong.

Spatial and Temporal Variability of Water Vapor Content during 1961-2011 in Tianshan Mountains,China

Based on the climate factors data and surface vapor pressure （SVP） data of 44 weather stations in Tianshan Mountains during the years 1961-2011, this paper establishes a water vapor content （WVC） estimation model according to the relationship between monthly WVC of radiosonde and corresponding SVP and analyzes the spatial and temporal variability of WVC and their causes. The results show that the WVC is linearly and negatively related to the elevation and longitude （Vertical zonality and Longitude zonality）, while it was not linearly related to the latitude. The westerly wind, geographical situation and sea level elevation composed complex surface conditions to influence the spatial distribution of WVC in the Tianshan Mountains. The Mann-Kendall （M-K） statistical test shows a significant increasing trend in the mean annual WVC in Tianshan Mountains during 1961- 2011（P 〈 0.001）, with a rate of 0.23 mm/decade, and indicates an abrupt turning point in 1985 （P.〈0.001）. Correlation analysis shows that the WVC are significantly correlated to the temperature, especially during the winter, but the summer WVC are significantly correlated to the precipitation. In addition, the North Atlantic Oscillation Index （NAOI） and the Arctic Oscillation Index （AOI） are significantly correlated to the winter WVC in the Tianshan Mountains. As a new Microwave radiometric profilers （MWRPs） instrument, the MP- 3000A provides continuous, real-time and high temporal resolution atmospheric profiles up to 10 km. In order to monitor water vapor and atmosphere profiles in Tianshan Mountains, an MP-3000A was established in Urumqi （43.8°N, 87.58°N） in May 2008. The results indicated that the MP-3oooA was applicable to this area, and the evolutionary process of water vapor and the WVC peak values of MP- 3000A were a strong signal for rainstorm and flood forecasts for Urumqi and the Tianshan Mountains.

Analysis on the Macro and Micro Physical Characteristics of Stratiform Cloud in Henan

By using the microphysical data of stratiform cloud in Henan which were observed by PMS airborne cloud particle measure system on March 23 in 2007 and combining with the radar,satellite,sounding data,the macro and micro physical structure characteristics of cloud were analyzed.The results showed that the average diameter of small cloud drop which was measured by FSSP-100 in the warm layer of cloud was mainly during 5-12 μm,and the average value was 7.33 μm.The biggest diameter of small cloud drop changed during 14-47 μm,and the average value was 27.80 μm.The total number concentration scope of small cloud drop was during 47.73-352.00 drop/cm3,and the average value was 160 drop/cm3.In the cold layer of cloud,the biggest diameter of small cloud particle(included the cloud droplet and the ice crystals)which was measured by FSSP-100 was 24.8 μm.The total number concentration scope of small cloud particle was during 0.899-641.000 drop/cm3,and the average value was 297 drop/cm3.The airborne King heat line liquid water content instrument observed that the super-cooling liquid water existed in the cloud.The super-cooling cloud water content changed during 0.02-0.20 g/m3,and the average value was 0.093 g/m3.The biggest value which was 0.202 g/m3 appeared in 4 368 m height(the temperature was-8.5 ℃).The particle spectrum type in the cloud was mainly the negative exponent type and the single peak type.

Global Water Vapor Content Decreases from 2003 to 2012： An Analysis Based on MODIS Data

Water vapor in the earth′s upper atmosphere plays a crucial role in the radiative balance, hydrological process, and climate change. Based on the latest moderate-resolution imaging spectroradiometer(MODIS) data, this study probes the spatio-temporal variations of global water vapor content in the past decade. It is found that overall the global water vapor content declined from 2003 to 2012(slope b = –0.0149, R = 0.893, P = 0.0005). The decreasing trend over the ocean surface(b = –0.0170, R = 0.908, P = 0.0003) is more explicit than that over terrestrial surface(b = –0.0100, R = 0.782, P = 0.0070), more significant over the Northern Hemisphere(b = –0.0175, R = 0.923, P = 0.0001) than that over the Southern Hemisphere(b = –0.0123, R = 0.826, P = 0.0030). In addition, the analytical results indicate that water vapor content are decreasing obviously between latitude of 36°N and 36°S(b = 0.0224, R = 0.892, P = 0.0005), especially between latitude of 0°N and 36°N(b = 0.0263, R = 0.931, P = 0.0001), while the water vapor concentrations are increasing slightly in the Arctic regions(b = 0.0028, R = 0.612, P = 0.0590). The decreasing and spatial variation of water vapor content regulates the effects of carbon dioxide which is the main reason of the trend in global surface temperatures becoming nearly flat since the late 1990 s. The spatio-temporal variations of water vapor content also affect the growth and spatial distribution of global vegetation which also regulates the global surface temperature change, and the climate change is mainly caused by the earth's orbit position in the solar and galaxy system. A big data model based on gravitational-magmatic change with the solar or the galactic system is proposed to be built for analyzing how the earth's orbit position in the solar and galaxy system affects spatio-temporal variations of global water vapor content, vegetation and temperature at large spatio-temporal scale. This comprehensive examination of water vapor changes promises a holistic understanding of the global climate change and potential underlying mechanisms.

GENERATION AND DEVELOPMENT OF MESOSCALE CLOUD ON HEAVY RAIN BELT ON THE PERIPHERY OF TYPHOON 9608 (Herb)

Typhoon-induced heavy rains are mostly studied from the viewpoint of upper-level westerly troughs. It is worthwhile to probe into a case where the rain is caused by tropical cyclone system, which is much heavier. During August 3 ~ 5, 1996, an unusually heavy rainstorm happened in the southwest of Hebei province. It was caused by 3 mesoscale convective cloud clusters on the periphery of a tropical cyclone other than the direct effects of a westerly trough. Generating in a weak baroclinic environment that is unstable with high energy, the cloud clusters were triggered off for development by unstable ageostrophic gravity waves in the low-level southeast jet stream on the periphery of the typhoon. There was a vertical circulation cell with horizontal scale close to 1000 km between the rainstorm area and westerly trough in northeast China. As shown in a computation of the Q vector of frontogenesis function, the circulation cell forms a mechanism of transforming energy between the area of interest and the westerly trough system farther away in northeast China. Study of water vapor chart indicates that high-latitude troughs in the northeast portion of the rain migrate to the southeast to enhance anti-cyclonic divergence in upper-level convection over the area of heavy rain and cause rain clusters, short-lived otherwise, to develop vigorously. It is acting as an amplifier in this case of unusually strong process of rain.

A Comparative Study of Cloud Liquid Water Content from Radiosonde Data at a Tropical Location

In this paper, some features of cloud liquid water content with respect to rain and water vapor are presented. Cloud liquid water density profile is obtained from radiosonde observation with Salonen's model and Karsten's model at Kolkata, a tropical location in the Indian region. Cloud liquid water contents (LWC) are obtained from these profiles which show a prominent seasonal variation. The monsoon months exhibit much higher values of LWC than in other months. However Salonen's model yields higher LWC values than that obtained with Karsten's model. The variation of daily total rainfall with LWC shows a positive relationship indicating the role of LWC in controlling the rainfall. Also the variation pattern of LWC with integrated water vapor (IWV) content of the atmosphere indicates that a threshold value of water vapor is required for cloud to form and once cloud is formed LWC increases with IWV.

New Cloud Detection Index (CDI) for Forecasting the Extreme Rain Events

The water vapor content and clouds play a very significant role in atmospheric conditions. This paper is derived from the new cloud detection index (CDI) which is useful to forecast extreme weather events like heavy or extreme rain. The CDI is retrieved using two crucial elements of cloud formation, the critical humidity and critical water vapor. The cloud thickness is determined by using CDI for a radiosonde site (VABB) located in Mumbai, the western part of India. The obtained results are compared with the cloud thickness required for extreme rain. The outcome of the comparison is discussed in this paper. The cloud detection index is also useful in establishing the atmospheric stability along with another four atmospheric stability indices.

An Improved 6S Code for Atmospheric Correction Based on Water Vapor Content

Water vapor content in the atmosphere is very significant for atmospheric correction of optical remote sensing data. Nowadays, the common atmospheric correction models use a single value of the average water vapor content of the study area to perform atmospheric correction. As the distribution of water vapor content varies greatly with time and space, it is obviously inaccurate to represent the total water vapor conditions of the whole area by just reading the average water vapor content. In this study, we altered the 6S sources so that it could read the water vapor content image which was retrieved from MODIS 1 km data. Atmospheric correction was implemented for the band 1 of MODIS 500 m data pixel-by-pixel using the improved 6S model. In comparison with the traditional 6S model, this improved 6S model is more reasonable in atmospheric correction, for it considers the spatial distribution of the water vapor content retrieved from MODIS data in the near infrared to define the atmospheric conditions for simulating the atmospheric radiative transfer. The results corrected by the improved 6S model showed more reasonable in pixel spatial distribution and closer histogram with the original image than those by traditional 6S model.

Properties of Cloud and Precipitation over the Tibetan Plateau

The characteristics of seasonal precipitation over the Tibetan Plateau （TP） were investigated using TRMM （Tropical Rain- fall Measuring Mission） precipitation data （3B43）. Sensitive regions of summer precipitation interannual variation anomalies were investigated using EOF （empirical orthogonal function） analysis. Furthermore, the profiles of cloud water content （CWC） and precipitable water in different regions and seasons were analyzed using TRMM-3A12 data observed by the TRMM Microwave Imager. Good agreement was found between hydrometeors and precipitation over the eastern and southeastern TP, where water vapor is adequate, while the water vapor amount is not significant over the western and northern TE Further analysis showed meridional and zonal anomalies of CWC centers in the ascending branch of the Hadley and Walker Circulation, especially over the south and east of the TE The interannual variation of hydrometeors over the past decade showed a decrease over the southeastern and northwestern TP, along with a corresponding increase over other regions.

Aircraft Observations of Liquid and Ice in Midlatitude Mixed-Phase Clouds

ABSTRACT This paper reports airborne measurements of midlatitude altostratus clouds observed over Zhengzhou, Henan Province, China on 3 March 2007. The case demonstrates mixed-phase conditions at altitudes from 3200 to 4600 m （0°C to -7.6°C）, with liquid water content ranging from 0.01 to 0.09 g m-3. In the observed mixed-phase cloud, liquid water content exhibited a bimodal distribution, whereas the maximum ice particle concentration was located in the middle part of the cloud. The liquid and ice particle data showed significant horizontal variability on the scale of a few hundred meters. The cloud droplet concentration varied greatly over the horizontal sampling area. There was an inverse relationship between the cloud droplet concentration and ice particle concentration. A gamma distribution provided the best description of the cloud droplet spectra. The liquid droplet distributions were found to increase in both size and concentration with altitude. It was inferred from the profile of the spectra parameters that the cloud droplet sizes tend to form a quasi-monodisperse distribution. Ice particle spectra in the cloud were fitted well by an exponential distribution. Finally, a remarkable power law relationship was found between the slope （λ） and intercept （No） parameters of the exponential size distribution.

Comparison of Cloud Properties between Cloud Sat Retrievals and Airplane Measurements in Mixed-Phase Cloud Layers of Weak Convective and Stratus Clouds

Cloud microphysical properties including liquid and ice particle number concentration （NC）, liquid water content （LWC）, ice water content （IWC） and effective radius （RE） were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear （Pl） and two exponential （P2 and P3） functions, which estimate the liquid-phase fraction as a function of subfreezing temperature （from -20℃ to 0℃）, were tested. The retrieved NC, LWC, IWC and RE using Pl were on average larger than airplane measurements in the same cloud layer, Function P2 performed better than p1 or P3 in retrieving the NCs of cloud droplets in the convective cloud, while function Pl performed better in the stratus cloud. Function P3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the Pl function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function P1.

Responses of Vertical Structures in Convective and Stratiform Regions to Large-Scale Forcing during the Landfall of Severe Tropical Storm Bilis (2006)

The responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis （2006） are investigated using the data from a two-dimensional cloud-resolving model simulation. An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds, which leads to -100% coverage of raining stratiform clouds over the entire model domain. The imposed forcing extends upward motion to the lower troposphere during 16-17 July, which leads to an enhancement of convective clouds and suppression of raining stratiform clouds. The switch of large-scale lower-tropospheric vertical velocity from weak downward motion on 15 July to moderate upward motion during 16-17 July produces a much broader distribution of the vertical velocity, water vapor and hydrometeor fluxes, perturbation specific humidity, and total hydrometeor mixing ratio during 16-17 July than those on 15 July in the analysis of contoured frequency-altitude diagrams. Further analysis of the water vapor budget reveals that local atmospheric moistening is mainly caused by the enhancement of evaporation of rain associated with downward motion on 15 July, whereas local atmospheric drying is mainly determined by the advective drying associated with downward motion over raining stratiform regions and by the net condensation associated with upward motion over convective regions during 16-17 July.

Magnitude and Trends of High-elevation Cloud Water Pollutant Concentrations and Modeled Deposition Fluxes

Cloud water samples, LWC （Liquid Water Content） and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 through 2011. This paper presents results from 2000 through the conclusion of the study in 2011. Samples were analyzed for SO42＂, NO3, NH4＋ and H＋. These measurements were supplemented by measurements of ambient air and precipitation concentrations to estimate dry and wet deposition. Cloud water concentrations, LWC, cloud frequency, various meteorological measurements and information on nearby forest canopy were used to model cloud water deposition to gauge trends in deposition. Total deposition was calculated as the sum of cloud, dry and wet deposition estimates. Concentrations and deposition fluxes declined over the study period. The decreases in cloud water SO42＂ and NO3 concentrations were 40 percent and 26 percent, respectively. Three-year mean 5042 and NO3 deposition rates decreased by 71 percent and 70 percent, respectively. Trends in concentrations and depositions were comparable with trends in SO2 and NOx emissions from Tennessee Valley Authority power plants and aggregated emission reductions from electric generating units in adjacent states. Back trajectories were simulated with the HYSPLIT model and aggregated over cloud sampling periods from 2000 through 2007 and 2009 through 2011. Trajectories during periods with high H＋ concentrations traveled over local EGU （Electric Generating Unit） emission sources in Tennessee and Kentucky to the Ohio River Valley, Alabama and Georgia with the conclusion that these source regions contributed to acidic cloud water deposition at Clingmans Dome. This work was supported by U.S. Environmental Protection Agency and the Tennessee Valley Authority with infrastructure support provided by the National Park Service.

Turbulent heat fluxes in the North Water Polynya and ice estimated based on ASRv2 data and their impact on cloud

The presence or absence of sea ice introduces a substantial perturbation to surface-atmosphere energy exchanges.Comprehending the effect of varying sea ice cover on surface-atmosphere interactions is an important consideration for understanding the Arctic climate system.The recurring North Water Polynya(NOW)serves as a natural laboratory for isolating cloud responses to a rapid,near-step perturbation in sea ice.In this study,we employed high-resolution Arctic System Reanalysis version 2(ASRv2)data to estimate turbulent heat fluxes over the NOW and nearby sea ice(NSI)area between 2005/2006 and 2015/2016.The results indicate that the average turbulent heat fluxes in the polynya are about 87%and 86%higher than in the NSI area over the 10 years during the entire duration of the polynya and during polar night,respectively.Enhanced turbulent heat fluxes from the polynya tend to produce more low-level clouds.The relationship between the polynya and low cloud in winter was examined based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO).The low-cloud fraction(0-2 km)was about 7%-34%larger over the polynya than the NSI area,and the ice water content below 200 m was about 250%-413%higher over the former than the latter.The correlation between cloud fraction and turbulent heat fluxes in the polynya peaks around the altitude of 200-300 m.These results suggest that the NOW affects the Arctic boundary layer cloudiness and structure in wintertime.Furthermore,higher horizontal resolution reanalysis data can advance our understanding of the cloud-polynya response.

Decoupling CO2 from Climate Change

This study determines if there is a correlation between rising carbon dioxide levels and global warming. Historical data were reviewed from three different time periods spanning 500 million years. It showed that the curves and trends were too dissimilar to establish a connection. Observations from CO2/temp ratios showed that the CO2 and the temperature moved in opposite directions 42% of the time. Many ratios displayed zero or near zero values, reflecting a lack of response. As much as 87% of the ratios revealed negative or near zero values, which strongly negate a correlation. The infrared spectra showed the Greenhouse Gases had an exceptionally low absorption band between 11.67 μm to 9.1 μm, which is a zone called the infrared atmospheric window. Most of the Greenhouse Gases absorb little infrared inside that zone. And that zone is where the Earth’s surface emits almost all infrared radiation. Even with minimal absorbance, water vapor captures the most infrared radiation. It absorbs 84 times more than CO2, 407 thousand times more than methane, 452 thousand times more than ozone and 2.3 million times more than nitrous oxide. The Intergovernmental Panel on Climate Change (IPCC) and the United States EPA excluded water vapor because it was not associated with man-made activities. They reported that water vapor and clouds were simply feedback mechanisms from CO2. Clouds reflect radiation from the sun. The Northern Hemisphere is 2.7°F warmer than the Southern Hemisphere because of clouds. The world cloud cover has gone down 4.1% from 1982 to 2018. Calculations show that this could be responsible for 2.4°F of the 2.7°F. The research shows that most of the recent increase in temperature (89.9%) is because of fewer clouds.

WATER VAPOR CONTENT AND MEAN TRANSFER IN THE ATMOSPHERE OVER NORTHWEST CHINA

The interannual and intermonthly climatic features of the water vapor content(hereafter WVC)and its mean transfer in the atmosphere over Northwest China(hereafter NWC)are calculated and analyzed by using the NCEP/NCAR global reanalysis grid data(2.5°×2.5°Lat/Lon) for 40 years(1958—1997).The results show that the WVC in the total air column over NWC in four seasons of the year is mainly concentrated on eastern and western NWC respectively.On the average,the WVC over eastern NWC decreases obviously during recent forty years except for winter.while it decreases over western NWC in the whole year.But the WVC over NWC has been increasing since late 1980s in summer.The water vapor comes from the southwestern warm and wet air current along the Yarlung Zangbo River Valley and the Bay of Bengal.and from mid- western Tibetan Plateau and also from the Qinling Mountains at southern Shaanxi Province.The yearly water vapor divergence appears over the middle of NWC to northern Xinjiang and southeastern Shaanxi Province.The yearly water vapor convergence appears over the Tarim Basin and the Tibetan Plateau as well as western Sichuan and southern Gansu.

东亚地区云微物理量分布特征的CloudSat卫星观测研究

本文利用2007～2010年整四年最新可利用的CloudSat卫星资料,对东亚地区（15°～60°N,70°～150°E）云的微物理量包括冰/液态水含量、冰/液态水路径、云滴数浓度和有效半径等的分布特征和季节变化进行了分析.本文将整个东亚地区划分为北方、南方、西北、青藏高原地区和东部海域五个子区域进行研究,结果显示：东亚地区冰水路径值的范围基本在700 g m-2以下,高值区分布在北纬40度以南区域,在南方地区夏季的平均值最大,为394.3 g m-2,而在西北地区冬季的平均值最小,为78.5 g m-2;而液态水路径的范围基本在600 g m-2以下,冬季在东部海域的值最大,达到300.8 g m-2,夏季最大值为281.5 g m-2,分布在南方地区上空.冰水含量的最高值为170 mg m-3,发生在8km附近,南方地区夏季的值达到最大,青藏高原地区的季节差异最大;而液态水含量在东亚地区的范围小于360 mg m-3,垂直廓线从10km向下基本呈现逐渐增大的趋势,峰值位于1～2 km高度上.冰云云滴数浓度在东亚地区的范围在150 L-1以下,水云云滴数浓度的值小于80 cm-3,垂直廓线的峰值均在夏季最大.冰云有效半径在东亚地区的最大值为90 μm,发生在5km左右;水云有效半径在东亚地区的值分布在10km以下,最大值为10～12 μm,基本位于1～2 km高度上.从概率分布函数来看,东亚地区冰/水云云滴数浓度的分布呈现明显的双峰型,其他量基本为单峰型.本文的结果可以为全球和区域气候模式在东亚地区对以上云微物理量的模拟提供一定的观测参考依据.

基于CloudSat卫星资料分析青藏高原东部夏季云的垂直结构

本文利用CloudSat卫星资料,对青藏高原东部2006-2010年6-8月云垂直结构的空间分布进行分析,结果表明：（1）夏季青藏高原东部云发展可达到平流层,且高原东部云在5km以下以水云存在,5-10km以液相和固相共存的混态存在,在垂直高度10km以上以冰云存在。由于CloudSat卫星资料云相的反演问题,可能会造成水云和混态云的发展上限偏低,冰云的发展下限抬升。（2）研究区整层水汽输送和云水平均路径空间分布存在一定的差异性,云水含量纬向分布表现为在26.5°-30.5°N附近存在一个明显的峰值区,经向分布表现为95°E以西云水含量低于以东。（3）研究区以单云层为主,尤其在青藏高原主体。单云层平均云层厚度4182 m,云顶高度、云厚限于水汽的输送,表现为由南向北波动下降。多层云发生频率在27°N以北明显减少,说明强烈的对流运动更容易激发多层云的产生。

利用NOAA-16/FY-1C和ASAR数据纠正大气水汽对重轨星载D-INSAR的影响

大气水汽影响一直是造成重轨星载合成孔径雷达差分干涉测量监测结果不确定性的一个重要因素.本文以地表形变速率稳定的延怀盆地为试验区,利用ASAR数据得到该区域的差分干涉处理结果,利用与ASAR数据获取时间相近的NOAA-16/FY-1C数据对该区域的大气水汽含量进行了反演.通过这些结果,对差分干涉处理结果中大气水汽的影响进行了去除.去除大气水汽影响后得到的地表形变结果与野外考察实测结果基本吻合,从而验证了该方法的可行性.