A year-round monitoring of sea ice properties from the AMSU satellite microwave radiometer data

A new approach to the year-round daily monitoring of sea ice properties based on the multispectral measurements of the AMSU satellite radiometer is considered. It is revealed that the increase in the values of the sea ice scattering index and its anomalously high variability are observed during the warm period of the year. The analysis of main reasons influencing the variations of the sea ice scattering index in different seasons is carried out. The recommendations are proposed on the identification of ice properties on the maps of the sea ice scattering index plotted for the warm, cold, and transition periods.     

Analysis of interrelation between the scattering index of sea ice and its properties

Analyzed is the interrelation between the properties of the sea ice, its scattering index at the frequencies of 23 and 31 GHz, and the brightness temperature computed from the multispectral measurements with the AMSU radiometer. Within the frameworks of the simplified model representations, the quantitative estimates are obtained of the influence of the ice thickness, ice concentration, and presence of inhomogeneities in the emitting layer and snow cover on the ice surface on the ice scattering index values. It is demonstrated that the scattering on the dislocations formed near the surface of ice at its bend and compression can be the main reason for the rapid change in the scattering index of one-year and old ice observed in different seasons. The results of the analysis corroborated the validity of applying the scattering index for the revelation of the areas of deformation and hummocking of sea ice, as well as for the estimation of the age and thickness of thin and young ice.     

Identification of the age and compression areas of sea ice from the AMSU satellite microwave radiometer data

A physical substantiation of the new quantitative index of sea ice scattering (Bukharov index) computed from the all-weather AMSU satellite radiometer data is considered. A high sensitivity of the scattering index to the age, thickness, and hummocking of ice in the areas of its compression is demonstrated. The daily maps of the sea ice scattering index in the Arctic are plotted. The analysis of maps enabled to reveal a new phenomenon, a steady existence of various-scale areas of short-range deformations of the sea ice in the Arctic. A new technique is proposed of the identification of age, relative thickness, and compression areas of ice using the maps of minimum and maximum values of the scattering index.     

Long-term observations for monitoring of the cryosphere

Variations of the cryosphere over decadal-to-century timescales are assessed by a survey of data on sea ice, snow cover, glaciers and ice sheets, permafrost and lake ice. The recent variations are generally consistent across the different cryospheric variables, especially when placed into the context of variations of temperature and precipitation. The recent warming over northern land areas has been accompanied by a decrease of snow cover, particularly during spring; the retreat of mountain glaciers is, in an aggregate sense, compatible with the observed warming; permafrost extent and lake ice duration show similar variations in areas for which data are available. Corresponding trends are not apparent, however, in data for some regions such as eastern Canada, nor in hemispheric sea ice data, especially for winter. The data also suggest an increase of snowfall over high latitudes, including the Antarctic ice sheet.Estimates of both the climatic and the statistical significance of the recent variations are hampered by data inhomogeneities, the shortness of the records of many variables and the absence of central archives for data on several variables. The potential of monitoring by satellite remote sensing has been realized with several variables (extent of sea ice, snow cover). Other cryospheric variables (snow depth, ice sheet elevation, lake ice, mountain glaciers) may be amenable to routine monitoring by satellites pending advances in instrumentation, modifications of satellite orbit, and further developments in signal detection algorithms. The survey of recent variations leads to recommendations concerning the use of historical data,in situ measurements, and remote sensing applications in the monitoring of the cryosphere.     

云量的时间精细化预报研究-以榆中为例

利用2001年7月至2011年7月甘肃省榆中县地面测站的每日8次云量资料和同期NCEP每日4次等压面资料,由NCEP资料构造预报因子,以总云量和低云量为预报对象,分析预报因子和预报对象的相关性,采用逐步回归方法建立榆中县逐月8个时次的云量预报方程并进行回代;并利用2012年的资料检验预报方程的预报效果。结果表明：云量主要受整层湿度、垂直运动、不稳定能量、槽强度指数和700 hPa水汽通量散度影响,其中湿度状况和垂直运动是重要因素。建立的预报方程对总云量的预报效果比低云量好;总云量平均预报误差在2成左右,低云量平均预报误差在3成左右;预报值变化趋势可以部分地反映实际云量的变化趋势。     

Identification of ice properties in the Sea of Okhotsk using scattering index maps

Considered are simplified model concepts allowing the use of the AMSU microwave radiometer measurement data and the maps of scattering index (SI) compiled by them for estimating the variability of the thickness of thin and young ice as well as for obtaining principally new satellite information about the areas of the possible hummocking of ice cover. Demonstrated is the essential influence of deep cyclones on the ice thickness reduction due to the ice thawing from below in the areas where waves are driven under the ice from the warmer, not frozen part of the water area. Carried out is a comparative analysis of sea ice properties identified from SI maps and the traditional maps of ice condition analysis. Noted is a possibility of the useful application of all-weather SI maps for monitoring sea ice properties in the areas of their rapid variability formed during the periods of a deep cyclone passage.     

城市雪灾气象等级划分标准的研究

选取累积降雪量、最大日降雪量、连续降雪日数、积雪深度、日最低气温、日最大风速和日最小相对湿度7个气象因子构成城市雪灾气象指数。通过对城市雪灾气象指数的范围划分,得到从低到高的5级城市雪灾气象等级,并给出等级描述及可能影响。     

城市雪灾气象等级划分标准的研究

摘要：本文选取累积降雪量、最大日降雪量、连续降雪日数、积雪深度、日最低气温、日最大风速和日最小相对湿度7个气象因子构成城市雪灾气象指数。通过对城市雪灾气象指数的范围划分,得到从低到高的5级城市雪灾气象等级,并给出等级描述及可能影响。     

江南春雨雨日的变化及其与欧亚大陆积雪的联系

利用中国气象局提供的1960—2019年江南区站点观测逐日降水数据,分析了江南春雨不同持续时长雨日的变化及其与欧亚大陆积雪的联系。结果表明,江南春雨以持续5 d及以上的长持续降水为主,但降水日数下降趋势明显,导致长持续降水减少。利用奇异值分解法(Singular Value Decomposition,SVD)发现,欧亚大陆3—5月积雪覆盖率与江南春雨雨日数有显著正相关关系。将(48°~59°N,90°~110°E)区域平均积雪覆盖率定义为积雪覆盖指数,通过指数与同期大气环流的回归分析发现,当积雪偏少时,我国中北部及西伯利亚地区500 hPa位势高度正异常,在江南区850 hPa风场和水汽通量场西南向负异常,导致江南春雨雨日数减少。合成分析进一步验证了积雪偏少会在江南区形成异常东北风抑制水汽输送至江南地区,不利于降水发生。     

利用ISCCP资料分析青藏高原云气候特征

利用ISCCP提供的1983年7月－1993年12月3h一次的月平均卫星决云量资料，将整个高原分为39个网格点，分析了高原总云量的年、季节、日变化规律及其空间分布特征，并根据高原水汽条件和地形动力影响以及环流特征作出一定的科学解释。将ISCCP总云量与地面观测总云量分布形势作了比较，证明了ISCCP－D2资料的合理性。对总云量与OLR进行相关分析，发现夏季相关好，冬季相关差。     

Insolation over the Arabian Sea during the southwest monsoon

The relationship between monsoon cloud cover and incoming solar radiation in the Arabian Sea is examined utilising the available observations of daily mean total cloud amount and solar radiation collected during the summer monsoon. With these data sets, various cloud correction formulae are evaluated. For the estimation of solar radiation, the formulation of Laevastu (1960) is best, with a minimum error of -4%. A multiple polynomial regression equation based on cloud cover and noon altitude of the sun is developed for estimation of daily radiation. The error between estimated and observed radiation is -2%.     

一个表征江南春雨的环流指数及其天气学特征

利用东亚和西太平洋对流层低层850 hPa纬向风的经向差异,定义了一个可以表征江南春雨变化特征的环流指数,通过诊断分析探讨该指数与降水和大气环流的关系。结果表明:该指数可以较好地反映江南春雨的年际和逐日变化特征。在年际时间尺度上,高指数年江南春雨偏多,而低指数年江南春雨偏少。该指数的逐日变化与江南地区同期逐日降水变化呈显著正相关。在高指数日,我国江南地区的低压系统和西北太平洋地区的副热带高压偏强,江南地区对流层高层辐散增强,低层辐合和高层辐散的增强为春雨发生提供动力抬升条件,有利于春季江南地区降水的产生;低指数日,西北太平洋副热带高压位置偏南,江南至华南地区对流层低层存在弱辐散,这种形势配合下不利于江南春雨的产生。     

北京上甸子秋冬季大气气溶胶的散射特征

分析了北京上甸子秋冬季气溶胶散射系数的变化特征、散射系数与PM2.5质量浓度的关系, 结合气象资料分析了风场对气溶胶散射系数变化的影响。通过研究得出, 上甸子秋冬季气溶胶散射系数平均值和标准差分别为179.7 Mm-1和253.2 Mm-1；阴天条件下的散射系数明显高于晴天；散射系数与PM2.5质量浓度之间有较好的相关性, 其相关系数为0.93；此外, 由于上甸子特殊的地理位置, 风场对气溶胶散射系数的影响显著, 不同风向条件下气溶胶散射系数差别很大。     

大气气溶胶散射吸湿增长特性研究进展

大气气溶胶的散射吸湿增长特性反映了相对湿度对气溶胶散射能力的影响。研究气溶胶散射吸湿增长对于评估气溶胶辐射强迫、了解气溶胶对大气能见度的影响具有重要意义。文中对气溶胶散射吸湿增长特性的研究意义、监测方法、中外研究进展、参数化拟合和模型模拟等方面进行了系统回顾和总结,并对未来发展方向做出展望。中国在该领域开展的研究数量偏少,广泛开展气溶胶散射吸湿增长特性研究十分必要。     

Variability and change in the Canadian cryosphere

During the International Polar Year (IPY), comprehensive observational research programs were undertaken to increase our understanding of the Canadian polar cryosphere response to a changing climate. Cryospheric components considered were snow, permafrost, sea ice, freshwater ice, glaciers and ice shelves. Enhancement of conventional observing systems and retrieval algorithms for satellite measurements facilitated development of a snapshot of current cryospheric conditions, providing a baseline against which future change can be assessed. Key findings include: 1. surface air temperatures across the Canadian Arctic exhibit a warming trend in all seasons over the past 40?years. A consistent pan-cryospheric response to these warming temperatures is evident through the analysis of multi-decadal datasets; 2. in recent years (including the IPY period) a higher rate of change was observed compared to previous decades including warming permafrost, reduction in snow cover extent and duration, reduction in summer sea ice extent, increased mass loss from glaciers, and thinning and break-up of the remaining Canadian ice shelves. These changes illustrate both a reduction in the spatial extent and mass of the cryosphere and an increase in the temporal persistence of melt related parameters. The observed changes in the cryosphere have important implications for human activity including the close ties of northerners to the land, access to northern regions for natural resource development, and the integrity of northern infrastructure.     

New approach to measure the stability of the solar radiative regime

This paper focuses on different ways of characterizing the solar radiative regime of a day and the stability of this regime. The days may be stratified in classes of cloud shade, observed total cloud cover amount, daily averaged clearness index, and fractal dimension of the solar global irradiance signal. A new Boolean parameter related to solar irradiance fluctuation is defined, namely the sunshine stability number. The time averaged value of the sunshine stability number is used for the characterization of the radiative regime stability during a given time interval. Ranking the days from the view-point of the stability of their radiative regime is performed by using the daily average value of the sunshine stability number and appropriately defined values of disorder and complexity, respectively. Measurements performed in the Romanian town of Timisoara (latitude 45°46?? N, longitude 21°25?? E and 85?m altitude above mean sea level) are used here. They refer to time series of global and diffuse solar irradiance recorded at 15-s time interval between sunrise and sunset during all the days in 2009.     

Evidence of climate change impact upon glaciers’ recession within the Italian Alps

We present evidence of climate change impact upon recent changes of glaciers within Lombardy region, in Northern Italy. We illustrate the recent area evolution of a set of 249 glaciers in the area using three surface area records for 1991, 1999 and 2003. The 1999 and 2003 surface area data are processed by combining glacier limits manually digitized upon registered color orthophotos and differential GPS (DGPS) glaciers’ surveys. Glaciers’ area was 117.4?km² in 1991, 104.7?km² in 1999, and to 92.4?km² 2003, with a 21% reduction. Glaciers smaller than 1?km² accounted for 53% of the total loss in area (13.1?km² during 1991–2003). The area change rate was higher lately, with ca. 11.7 % reduction during 1999–2003. We split Alps and fore Alps of Lombardy into six mountain groups, and we separately investigate relative area variations. We use climate series from local stations within each group to assess climate change during a 30-year window (1976–2005). We focus upon temperature and snow cover depth at thaw, known to impact glaciers’ changes. We compare local year-round temperature anomalies against global ones to evidence enhanced warming within this area, and we investigate the correlation of our target climate variables against NAO. Eventually, we highlight the link between the rate of change of our climate variables to the observed scaling of area loss against glaciers’ size, showing that in rapidly warming areas glaciers’ size affects less relative melting.     

Parametrization schemes of incident radiation in the North Water polynya

Abstract

An evaluation of the Canadian Land Surface Scheme (CLASS) 3.1 snow cover simulations at four sites included in the Snow Model Intercomparison Project (SnowMIP) revealed that CLASS was able to provide realistic representations of snow cover accumulation, melt and physical properties over a range of snow cover climates. The modified snow aging parametrization in CLASS 3.1 provided improved simulations of snowpack density which resulted in a marked reduction in the root‐mean‐square (rms) error for daily snow depth, and slight improvements in snow surface temperature. CLASS 3.1 still exhibited a tendency to overestimate snow cover duration which is attributed to the way shallow snow ablation is treated. CLASS provided generally realistic simulations of daily and seasonal variation in snow albedo although cold snow albedo was underpredicted by 0.10 to 0.15 at a site with a deep (> 2 m) cold snowpack. CLASS also exhibited a tendency to overpredict late spring snow albedo which was reduced by the addition of a snow layer subroutine that kept track of snow albedo by precipitation event. CLASS had a noticeable cold bias averaging 3°–4°C at two mountain sites included in the comparison. The bias was closely linked to atmospheric stability and could exceed 10°C under conditions of strong radiative cooling and low wind speeds. The CLASS energy deficit under these conditions was determined to be ～20–40 W m^?2 and was mostly accounted for by introducing a windless exchange coefficient into the calculation of sensible heat fluxes following the approach used in a number of other physical snowpack models. CLASS provided realistic simulations of daily snowmelt runoff with the exception of the Weissfluhjoch site which was characterized by a deep cold snowpack. A preliminary assessment of snow water equivalent (SWE) rms error for the 23 models participating in SnowMIP showed that CLASS was one of the better single layer snow models included in the comparison. CLASS performance was comparable to the multi‐layer CROCUS snowpack model in the evaluations carried out in this study.     

Scattering Properties of Atmospheric Aerosols over Lanzhou City and Applications Using an Integrating Nephelometer

The data, measured by a three-wavelength Integrating Nephelometer over Lanzhou City during the winters of 2001/2002 and 2002/2003 respectively, have been analyzed for investigating the scattering properties of atmospheric aerosols and exploring their relationship and the status of air pollution. The aerosol particle volume distribution is inverted with the measured spectral scattering coefficients. The results show that the daily variation of the aerosol scattering coefficients is in a tri-peak shape. The average ratio of backscattering coefficient to total scattering coefficient at 550 nm is 0.158; there exists an excellent correlation between the scattering coefficients and the concentration of PM10. The average ratio of the concentration of PM10 to the scattering coefficients is 0.37 g m-2, which is contingent on the optical parameters of aerosol particles such as the size distribution, etc.; an algorithm is developed for inverting the volume distribution of aerosol particles by using the histogram and Monte-Carlo techniques, and the test results show that the inversion is reasonable.     

Scattering Properties of Atmospheric Aerosols over Lanzhou City and Applications Using an Integrating Nephelometer

The data, measured by a three-wavelength Integrating Nephelometer over Lanzhou City during the winters of 2001/2002 and 2002/2003 respectively, have been analyzed for investigating the scattering properties of atmospheric aerosols and exploring their relationship and the status of air pollution. The aerosol particle volume distribution is inverted with the measured spectral scattering coefficients. The results show that the daily variation of the aerosol scattering coefficients is in a tri-peak shape. The average ratio of backscattering coefficient to total scattering coefficient at 550 nm is 0.158; there exists an excellent correlation between the scattering coefficients and the concentration of PM10. The average ratio of the concentration of PM10 to the scattering coefficients is 0.37g m^-2, which is contingent on the optical parameters of aerosol particles such as the size distribution, etc.; an algorithm is developed for inverting the volume distribution of aerosol particles by using the histogram and Monte-Carlo techniques, and the test results show that the inversion is reasonable.