Comparing carbon accumulation in restored and natural wetland soils of coastal Louisiana

Louisiana's chronic wetland deterioration has resulted in massive soil organic matter loss and subsequent carbon release through oxidation. To combat these losses, and reestablish ecosystem function, goods, and services, many restoration projects have been constructed or planned throughout coastal Louisiana. There are significant data gaps and conflicting results regarding wetland contributions to global warming, especially related to carbon sequestration in restored wetlands. An exceptionally large data set was used to derive carbon accumulation rates from key soil characteristics and processes. Assessments and comparisons of bulk density, organic matter, total carbon, vertical accretion (short- and longer-term), and carbon accumulation rates were made across time (chronosequence) and space (i.e., coastwide, watershed basins, and vegetation zones). Carbon accumulation rates in the Louisiana coastal zone were generally correlated to hydrogeomorphology, with higher rates occurring in zones of high river connectivity or in swamp or higher salinity tolerant marsh. On average, naturally occurring wetlands had higher carbon accumulation rates than restoration sites. Although some restoration measures were higher, and most showed increasing carbon accumulation rates over time. Results demonstrate that although wetland restoration provides many ecosystem benefits, the associated carbon sequestration may also provide useful measures for climate change management.     

Suitability mapping of global wetland areas and validation with remotely sensed data

With increasing urbanization and agricultural expansion, large tracts of wetlands have been either disturbed or converted to other uses. To protect wetlands, accurate distribution maps are needed. However, because of the dramatic diversity of wetlands and difficulties in field work, wetland mapping on a large spatial scale is very difficult to do. Until recently there were only a few high resolution global wetland distribution datasets developed for wetland protection and restoration. In this paper, we used hydrologic and climatic variables in combination with Compound Topographic Index(CTI) data in modeling the average annual water table depth at 30 arc-second grids over the continental areas of the world except for Antarctica. The water table depth data were modeled without considering influences of anthropogenic activities. We adopted a relationship between potential wetland distribution and water table depth to develop the global wetland suitability distribution dataset. The modeling results showed that the total area of global wetland reached 3.316×107 km2. Remote-sensing-based validation based on a compilation of wetland areas from multiple sources indicates that the overall accuracy of our product is 83.7%. This result can be used as the basis for mapping the actual global wetland distribution. Because the modeling process did not account for the impact of anthropogenic water management such as irrigation and reservoir construction over suitable wetland areas, our result represents the upper bound of wetland areas when compared with some other global wetland datasets. Our method requires relatively fewer datasets and has a higher accuracy than a recently developed global wetland dataset.     

Current state of knowledge regarding South America wetlands and their future under global climate change

The exact size of the wetland area of South America is not known but may comprise as much as 20% of the sub-continent, with river floodplains and intermittent interfluvial wetlands as the most prominent types. A few wetland areas have been well studied, whereas little is known about others, including some that are very large. Despite the fact that most South American countries have signed the Ramsar convention, efforts to elaborate basic data have been insufficient, thereby hindering the formulation of a wetland-friendly policy allowing the sustainable management of these areas. Until now, the low population density in many wetland areas has provided a high level of protection; however, the pressure on wetland integrity is increasing, mainly as a result of land reclamation for agriculture and animal ranching, infrastructure building, pollution, mining activities, and the construction of hydroelectric power plants. The Intergovernmental Panel on Climate Change has predicted increasing temperatures, accelerated melting of the glaciers in Patagonia and the Andes, a rise in sea level of 20–60 cm, and an increase in extreme multiannual and short-term climate events (El Niño and La Niña, heavy rains and droughts, heat waves). Precipitation may decrease slightly near the Caribbean coast as well as over large parts of Brazil, Chile, and Patagonia, but increase in Colombia, Ecuador, and Peru, around the equator, and in southeastern South America. Of even greater impact may be a change in rainfall distribution, with precipitation increasing during the rainy season and decreasing during the dry season. There is no doubt that the predicted changes in global climate will strongly affect South American wetlands, mainly those with a low hydrologic buffer capacity. However, for the coming decades, wetland destruction by wetland-unfriendly development planning will by far outweigh the negative impacts of global climate change. South American governments must bear in mind that there are many benefits that wetlands bring about for the landscape and biodiversity as well as for humans. While water availability will be the key problem for the continent’s cities and agroindustries, intact wetlands can play a major role in storing water, buffering river and stream discharges, and recharging subterranean aquifers.     

全新世以来东北地区沼泽湿地发育过程及其对气候变化的响应

沼泽湿地是陆地生态系统的重要组成部分,在维护区域环境稳定中起着重要作用.随着社会经济的发展,人类活动导致湿地大面积退化和消失,严重影响了区域生态安全;恢复退化湿地已成为各国政府和学者关注的焦点.而了解历史时期沼泽湿地发育过程及影响因素则是建立合理湿地恢复目标的重要前提.东北地区是我国最大的沼泽湿地集中分布区,其中70%的湿地面临不同程度的退化威胁;但由于数据的缺乏,东北地区沼泽湿地发育过程及其与气候变化的关系仍不清楚.基于此,本研究系统分析了全新世以来东北地区沼泽湿地形成发育的动态变化过程,并探讨了东北地区不同区域沼泽湿地的发育规律及其对气候变化的响应机理.研究发现东北地区沼泽湿地约从12 ka（1 ka=1000 cal.）开始发育,在距今8.6 ka以后开始广泛形成,约有35%的沼泽湿地形成于全新世暖湿期（8.0-4.0 ka）;而沼泽湿地发育的高峰期则集中在全新世晚期.这种发育趋势与全球北方主要区域沼泽湿地大规模发育趋势显著不同.古气候重建表明,全新世早期东北地区气候温暖湿润,处在有利于沼泽发育的时期,促进了沼泽湿地的形成;而在全新世晚期,东北地区呈现冷湿的气候组合特征,冷湿的气候条件不利于有机质的分解,进而促进了沼泽湿地的大规模形成和发育.此外,研究结果也表明全新世以来东北地区不同区域沼泽湿地发育的时间和规模呈现显著的空间差异,而温度和降水则是影响不同区域沼泽湿地发育的最重要因素.本研究将为我国东北地区沼泽湿地的保护和恢复提供一定的理论和数据支持.     

Future of wetlands in tropical and subtropical Asia, especially in the face of climate change

Tropical and subtropical Asia differs from other tropical regions in its monsoonal climate and the dominant influence of the Hindukush and Himalayan mountain ranges which result in extremes of spatial and temporal variability in precipitation. However, several major rivers and their tributaries arise in the Himalayan ranges and are fed by thousands of glaciers. Huge sediment loads carried by these rivers result in important deltas at their mouths. The climatic and physiographic diversity have endowed the region with many kinds of wetlands. Of these, the peatswamps of southeast Asia constitute about 56% of the world’s tropical peatlands, and more than 42% of the world’s mangroves occur in South and southeast Asia. Among other wetlands, riverine swamps are rather restricted whereas the seasonal marshes are a dominant feature. Another characteristic feature of tropical Asia are the innumerable human-made and intensively managed wetlands of which the paddy fields and aquaculture ponds are the most extensive. Throughout tropical Asia, wetlands have been a part of the socio-cultural ethos of the people and many communities have lived in wetlands. However, the pressures of high population and the economic development have extensively impacted upon wetlands which have been transformed for paddy cultivation and aquaculture, drained and converted to other land uses for economic gains (e.g., conversion to oil palm), and degraded by discharge of domestic and industrial wastes. Invasive plant and animal species have also played a significant role. The climate change is already being felt in the rapid retreat of Himalayan glaciers, increased temperature and variability in precipitation as well as the frequency of extreme events. Sea level rise is seen as a major threat to the coastal wetlands, particularly the mangroves. Increasing droughts have caused frequent fires in Indonesian peat swamps that have further feedback impacts on regional climate. However, the actual threat to wetlands in this region arises from the extensive hydrological alterations being caused by storage, abstraction and diversion of river flows for agriculture, industry and hydropower. Currently, the state of our understanding wetlands in general, and the efforts and infrastructure for research and training in wetlands are very poor. Although a few wetlands have been designated as Ramsar sites, the policies aimed at wetland conservation are either non-existent or very weak. Human responses to greater uncertainty and variability in the available water resources in different parts of Asia will be crucial to the conservation of wetlands in the future.     

西洞庭湖季节性淹水和植被类型对温室气体排放通量的影响

植被类型及淹水带来的干湿交替过程是影响温室气体排放的重要因素.本文通过原状土柱模拟实验,模拟西洞庭湖水文节律变化对不同土壤—植被系统温室气体排放的影响.利用静态箱—气相色谱法研究不同植被—土壤类型(芦苇湿地、灰化苔草湿地和刚砍伐的杨树林湿地)在季节性淹水条件下的CO₂、CH₄和N₂O的排放通量变化,并探讨了在水位变化的情况下,不同植被—土壤类型对全球增温潜势的贡献.结果表明:在不同的水文条件下,芦苇湿地的CO₂排放通量均显著高于苔草和杨树林湿地;淹水过程导致3种植被类型覆盖湿地CO₂排放通量显著降低,甲烷排放通量升高,其中芦苇湿地CH₄排放通量升高显著,苔草和杨树林湿地CH₄排放通量升高不明显;水文变化及植被类型对N₂O排放通量的影响不显著;不同植被类型湿地对全球增温潜势的贡献为:芦苇>杨树林>苔草,分别为16191.3、3405.6和1883.1 kg/hm².本研究结果表明在...     

WETLAND LOSS IN COASTAL LOUISIANA

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Wetlands with controlled drainage and sub‐irrigation systems—modelling of the water balance

Over the past centuries, the agricultural use of wetlands in Central Europe has required interference with the natural wetland water balance. Often this has consisted of drainage measures alone. In low‐precipitation areas, it has also involved the operation of combined drainage and sub‐irrigation systems. Model studies conducted as part of planning processes, or with a view to finding out the impact of changing climate conditions on the water balance of wetlands, must take these facts into account. For this reason, a water balance model has been devised for wetlands whose water balance is governed by water resources management systems. It is based on the WBalMo model system. Special modules were integrated into WBalMo to calculate the water balance of wetland areas (WABI module) and to regulate inflow partitioning within the wetland (REGINF module). When calculating the water balance, the WABI module takes into account precipitation and potential evapotranspiration, groundwater levels below surface, soil types, land‐use classes, inflows via the running water system, and data for target water levels. It provides actual evapotranspiration, discharge into the running water system, and groundwater levels in the area. The example of the Spreewald, a major wetland area in north‐eastern Germany, was used to design and test the WBalMo Spreewald model. The comparison of measured and calculated water balance parameters of the wetland area confirms the suitability of the model for water balance studies in wetlands with complex water resources management systems. The results reveal the strong influence of water management on the water balance of such areas. The model system has proved to be excellently suited for planning and carrying out water management measures aimed at the sustainable development of wetlands. Furthermore, scenario analyses can be used to assess the impact of global change on the water balance of wetlands. Copyright © 2006 John Wiley & Sons, Ltd.     

Recent glacial retreat in High Asia in China and its impact on water resource in Northwest China

There are about 46298 glaciers in the High Asiain China, the total glacial area is about 59406 km , andtotal glacial volume about 5590 km3. These glaciersmainly concentrate around the Himalayas Mountains,Nyainqentanglha Mountains, Kunlun Mountains,Karakoram Mountains and Tianshan Mountains. Theglaciers in the Tibetan Plateau are the major compo-nent of the glaciers in the High Asia in China. Theseglaciers extend north to the arid and desert regions,and become the main water resource in …     

Estimating restorable wetland water storage at landscape scales

Globally, hydrologic modifications such as ditching and subsurface drainage have significantly reduced wetland water storage capacity (i.e., volume of surface water a wetland can retain) and consequent wetland functions. While wetland area has been well documented across many landscapes and used to guide restoration efforts, few studies have directly quantified the associated wetland storage capacity. Here, we present a novel raster‐based approach to quantify both contemporary and potential (i.e., restorable) storage capacities of individual depressional basins across landscapes. We demonstrate the utility of this method by applying it to the Delmarva Peninsula, a region punctuated by both depressional wetlands and drainage ditches. Across the entire peninsula, we estimated that restoration (i.e., plugging ditches) could increase storage capacity by 80%. Focusing on an individual watershed, we found that over 59% of restorable storage capacity occurs within 20 m of the drainage network, and that 93% occurs within 1 m elevation of the drainage network. Our demonstration highlights widespread ditching in this landscape, spatial patterns of both contemporary and potential storage capacities, and clear opportunities for hydrologic restoration. In Delmarva and more broadly, our novel approach can inform targeted landscape‐scale conservation and restoration efforts to optimize hydrologically mediated wetland functions.     

高亚洲冰川质量变化趋势的卫星重力探测

利用高亚洲地区32个Mascon,基于GRACE RL05时变重力场模型频域和空域上的两种计算方法有效分离并提取出高亚洲冰川及其毗邻地区的等效水质量变化,得到2002—2013年期间高亚洲地区更为可靠的Mascon质量变化.高亚洲冰川质量变化的空间特征是:青藏高原内陆地区以正增长为主,边缘地区以负增长为主,在藏东南的最边缘地区冰川质量损失最为严重.天山地区、帕米尔和昆仑山地区、喜马拉雅山和喀喇昆仑山地区、青藏高原内陆地区冰川质量的平均变化趋势分别为-2.8±0.9 Gt/a、-3.3±1.5 Gt/a、-9.9±2.1 Gt/a和5.0±0.8 Gt/a, 高亚洲冰川质量整体的平均变化趋势为-11.0±2.9 Gt/a.印度等北部平原地区地下水平均变化趋势为-35.0±4.2 Gt/a,该地区地下水信号泄漏是影响GRACE研究高亚洲冰川质量变化的关键因素,频域法和空域法能有效改正该地区地下水信号泄漏的影响.     

New mapping techniques to estimate the preferential loss of small wetlands on prairie landscapes

Reliable estimates of wetland loss require improved wetland inventories and effective monitoring programmes. The Prairie Pothole Region of North America is experiencing rapid urban, agricultural and economic development, which places wetlands at risk, especially small geographically isolated wetlands. This loss is concomitant with a loss of ecosystem services. To improve upon current wetland inventories, a method for mapping wetlands using an automated object‐based approach was developed for a regional watershed in Alberta. The method improves upon existing wetland mapping methods by effectively mapping small wetlands and better capturing the convolution of wetland edges. This approach uses digital terrain objects derived from light detection and ranging data, from which 130 157 wetlands were identified. Wetland loss estimates (% number and % area) were obtained by applying a wetland area versus frequency power‐law function to the wetland inventory. We estimated a 16.2% historic loss of wetland number and a 2.6% loss of wetland area, with the size of these lost wetlands <0.04 ha. The improved techniques for mapping wetland loss and estimating wetland loss provide a more accurate representation of the magnitude of wetland loss in the Prairie Pothole Region. Copyright © 2015 John Wiley & Sons, Ltd.     

The filtering capacity of a tropical riverine wetland: II. Sediment and nutrient balances

The ability of wetlands to improve the quality of water has long been recognized and has led to the proliferation of wetlands as a means to treat diffuse and point source pollutants from a range of land uses. However, much of the existing research has been undertaken in temperate climates with a paucity of information on the effectiveness of wetlands, particularly natural wetlands, in tropical regions. This paper contributes to addressing this issue by presenting a comprehensive measurement based assessment of the potential for a naturally occurring tropical riverine wetland to improve the quality of the water entering it. We found small net imports and exports of sediment to/from the wetland in individual years, but over the longer term this kind of wetland is neither a sink nor source of sediment. In contrast, phosphorus was continually removed by the wetland with an overall net reduction of 14%. However, it should be noted that there is no ‘permanent’ gaseous loss mechanism for phosphorus, and its removal from the water column is equal to its accumulation in the wetland soil. We found very little removal of nitrogen by this type of wetland from several analyses including: (i) Surface and groundwater fluxes, (ii) Estimation of water column and soil denitrification rates, (iii) Wetland residence times, and (iv) Hydraulic loading. We also found no clear evidence for transformation of nitrogen to more or less bio‐available forms. Hence, while the benefits of using wetlands to improve water quality in controlled environments have been demonstrated in the literature, these benefits may not always be directly translated to unmanaged natural wetland systems when there is strong seasonality in flows and short residence time during the periods of maximum sediment and nutrient load. Copyright © 2011 John Wiley & Sons, Ltd.     

Evaluating the sensitivity of wetlands to climate change with remote sensing techniques

Wetlands are valuable ecosystems that provide many valuable services, yet many of these important ecosystems are at risk because of current trends in climate change. The Prairie Pothole Region (PPR) in the upper‐midwest of the United States and south‐central Canada, characterized by glacially sculpted landscapes and abundant wetlands, is one such vulnerable region. According to regional/global climate model predictions, drought occurrence will increase in the PPR region through the 21st century and thus will probably cause the amount of water in wetlands to decline. Water surface area (WSA) of Kidder County, ND, from 1984–2011 was measured by classifying TM/ETM+(Landsat Thematic Mapper / Enhanced Thematic Mapper Plus) images through the modified normalized difference water index. We then developed a linear model based on the WSA of these wetlands and historical climate data and used this to determine the wetland sensitivity to climate change and predict future wetlands WSA in the PPR. Our model based on Palmer drought severity index (PDSI) of the current year (PDSI_{t ? 0}) and of the previous two years (PDSI_{t ? 2}) can explain 79% of the annual wetland WSA variance, suggesting a high sensitivity of wetlands to drought/climate change. We also predicted the PPR wetlands WSA in the 21st century under A1B scenario (a mid‐carbon emission scenario) using simulated PDSI based on Intergovernmental Panel on Climate Change AR4 22‐model ensemble climate. According to our prediction, the WSA of the PPR wetlands will decrease to less than half of the baseline WSA (defined as the mean wetlands WSA of the 2000s) by the mid of the 21st century, and to less than one‐third by the 2080s, and will then slightly increase in the 2090s. This considerable future wetland loss caused only by climate change provides important implication to future wetland management and climate adaptation policy. Copyright © 2012 John Wiley & Sons, Ltd.     

湖泊湿地水文过程研究进展

湖泊湿地是世界上最重要的生态系统之一,在调蓄洪水、净化环境、保护生物多样性以及为人类提供淡水和食物等方面发挥着不可替代的作用.然而,受气候变化和人类活动叠加影响,湖泊湿地水文过程发生了剧烈变化,湖泊湿地面临着面积萎缩、质量下降和服务功能退化等风险.本文总结了原位观测、数值模拟和遥感技术在获取湖泊湿地关键水文要素方面的优...     

High Arctic wetlands: Their occurrence, hydrological characteristics and sustainability

High Arctic wetlands, though limited in occurrence, are an important ecological niche, providing the major vegetated areas in an arid and cold polar desert environment. These wetlands are often found as patches in the barren landscape. At a few locales which may be ice-wedge polygonal grounds, glacial terrain and zones of recent coastal uplift, wetland occurrence can become extensive, forming a mosaic that comprises patches of different wetland types. Reliable water supply during the thawed season is a deciding factor in wetland sustainability. The sources include meltwater from late-lying snowbanks, localized ground water discharge, streamflow, inundation by lakes and the sea, and for some ice-wedge wetlands, ground-ice melt. Different types of wetlands have their own characteristics, and peat accumulation or diatom depositions are common. The peat cover insulates the wetland from summer heating and encourages permafrost aggradation, with the feedback that a shallow frost table reduces the moisture storage capacity in a thinly thawed layer, which becomes easily saturated. All the wetlands studied have high calcium content since they are formed on carbonate terrain. Coastal wetlands have high salt concentration while snowmelt and ground-ice melt provides dilution. The sustainability of High Arctic wetlands is predicated upon water supply exceeding the losses to evaporation and lateral drainage. Disturbances due to natural causes such as climatic variations, geomorphic changes, or human-induced drainage, can reduce inundation opportunities or increase outflow. Then, the water table drops, the vegetation changes and the peat degrades, leading to the detriment of the wetlands.     

Actual state of European wetlands and their possible future in the context of global climate change

The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetlands to ongoing climate change will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands, especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to increased annual evapotranspiration and lower organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may strengthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other.     

Is net ecosystem production higher in natural relative to constructed wetlands?

Ecosystem metabolism is an important measure of wetland restoration efficiency, and serves to indicate if the system is capable of processing energetic resources. Despite its value, ecosystem metabolism has rarely been included in monitoring programs. In this study, we aimed to achieve the following objectives: (i) compare net ecosystem production (NEP) rates of constructed vs. natural wetlands; (ii) identify the highest NEP rate habitats; and (iii) define the main environmental factors regulating NEP in different wetland types. Pelagic and benthic NEP rates and physicochemical features were measured in three natural and five constructed wetlands in the middle Ebro River floodplain (NE Spain). Statistical analyses showed pelagic NEP rates peaked in natural wetlands, which produced up to 187.5 mg C m^?3 h^?1 compared to lower rates in constructed wetlands (up to 46.2 mg C m^?3 h^?1). Pelagic NEP responded positively to temperature, total dissolved solids, and nutrients. Benthic NEP rates were 3 to 30-fold greater than pelagic in natural (up to 994.9 mg C m^?3 h^?1) and constructed (up to 1,551.5 mg C m^?3 h^?1) wetlands, and were heavily influenced by habitat type, with NEP peaking in areas dominated by submerged vegetation and fine organic sediment. Rapid recovery in aquatic communities (i.e. macroinvertebrate diversity) has been previously reported for the studied wetlands; however, our study suggests a slower recovery of functional processes (i.e. pelagic NEP) in constructed habitats. We therefore strongly advocate the inclusion of ecosystem function in the design and evaluation of restoration projects to optimise long-term wetland ecosystem sustainability.     

Development of a SWAT extension module to simulate riparian wetland hydrologic processes at a watershed scale

Using a mass balance algorithm, this study develops an extension module that can be embedded in the commonly used Soil and Water Assessment Tool (SWAT). This module makes it possible to assess effects of riparian wetlands on runoff and sediment yields at a watershed scale, which is very important for aquatic ecosystem management but rarely documented in the literature. In addition to delineating boundaries of a watershed and its subwatersheds, the module groups riparian wetlands within a subwatershed into an equivalent wetland for modelling purposes. Further, the module has functions to compute upland drainage area and other parameters (e.g. maximum volume) for the equivalent wetland based on digital elevation model, stream network, land use, soil and wetland distribution GIS datasets. SWAT is used to estimate and route runoff and sediment generated from upland drainage area. The lateral exchange processes between riparian wetlands and their hydraulically connected streams are simulated by the extension module. The developed module is empirically applied to the 53 km² Upper Canagagigue Creek watershed located in Southern Ontario of Canada. The simulation results indicate that the module can make SWAT more reasonably predict flow and sediment loads at the outlet of the watershed and better represent the hydrologic processes within it. The simulation is sensitive to errors of wetland parameters and channel geometry. The approach of embedding the module into SWAT enables simulation of hydrologic processes in riparian wetlands, evaluation of wetland effects on regulating stream flow and sediment loading and assessment of various wetland restoration scenarios. Copyright © 2008 John Wiley & Sons, Ltd.     

Climatology of yellow sand (Asian sand,Asian dust or Kosa) in East Asia

In order to study climatology of yellow sand (Asian sand, Asian dust or Kosa) in East Asia, secular fluctuation in China, Korea and Japan in the recent 30 years was presented. The number of days with sand-dust storm at five stations in China—Hotan, Zhangye, Minqin, Jurh and Beijing, decreases a lot at the former three stations, but changed little at the latter two stations. Suggesting that the recent global warming is more evident in Xinjiang and Gansu, where the frequency of cold air invasions from the higher latitudes is decreasing. But, the eastern parts of Mongolia, inner Mongolia, and North China encounter stronger cyclones in early spring as a result of global warming. These cyclones bring cold air from higher latitudes, causing severe dust storms. Secular variation in the annual days with sand-dust storms in China and Kosa days in Korea and Japan show a parallel change with higher frequency from 1975 to 1985. This may be related to the higher frequency of La Nina years. However, different tendency was shown in the period from 1986 to 1996. Since 1996 or 1997, a sharp increase is clear, which may be caused by the developed cyclones in East Asia as well as human activities, and stronger land degradation under La Nina conditions. Anomalies of the total number of stations with Kosa days were discussed in accordance with some synoptic meteorological conditions such as the differences between Siberian anticyclone and Aleutian cyclone center at 500 hPa level during the previous winter.