Wetlands are the primary natural source of methane (CH4) emissions to the atmosphere, however, the quantification of wetland CH4 flux and net carbon budgets remains uncertain due to limited measurements and large variability across different types of wetlands. Based on continuous measurements using the eddy covariance (EC) technique over a "floating blanket" wetland in southwest China for a period of over three years (2018-2021), we examined the temporal variations of CH4 flux and its environmental controls on different temporal scales. The results showed that this wetland acted as a sink for carbon dioxide (CO2) while simultaneously serving as a source for CH4. The annual CO2 uptake and CH4 emission was 155.9-221.2 g C-CO2 m(-2) yr(-1) and 44.6-56.9 g CCH4 m(2) yr(-1) during 2019-2021, respectively. The annual total carbon budget varied from -176.6 g C m(2) yr(-1) to -99.0 g C m(2) yr(-1). From half-hourly to monthly timescales, CH4 flux was mainly controlled by water temperature with a positive correlation. There was a negative correlation between CH4 flux and CO2 flux, and the importance of CO2 flux to CH4 flux increased as the timescale extended. CH4 flux exhibited a significant positive correlation with the ecosystem gross primary production (GPP) and respiration (Re) on daily and monthly timescales. In addition, the fraction of vegetation cover had a positive impact on CH4 emissions. There was a significant variation in the fraction of vegetation cover with wind direction. The southwestern wind sector had the highest fraction of vegetation cover compared to other sectors, leading to the formation of the CH4 emission hotspot. The cumulative CH4 emissions in the southwestern wind sector were also higher than those in other sectors, accounting for around 58.13% of the annual total CH4 emissions, while the cumulative CH4 emissions in other wind sectors accounted for 5.21%-21.50%.

采用WRF模式模拟了云南省哀牢山区域2020年6月13～14日一次降水过程.通过不同高度的地形敏感性试验对比分析,讨论了哀牢山地形对强降水时空分布的影响及可能的物理机制.研究结果发现:1)不同高度的地形敏感性试验表明,地形高度对低涡切变线的位置有影响.2)地形升高后,中低层的假相当位温线更密集且梯度较大,水汽与不稳定能量迅速堆积,伴随的强上升运动可能会提前触发强对流天气;地形高度降低后,则假相当位温线平直且疏散;哀牢山局地抬升作用与不稳定能量较小,且不足以触发中小尺度强对流天气.3)在WSM6微物理方案下,地形高度的变化亦对云微物理过程有明显的影响.地形升高后强迫抬升作用加强,使中高层的冰晶与雪混合物在空中停留的时间更长而扩展范围逐步增大;从而产生次级环流的下沉气流,中低层云水和雨滴碰并增强,造成云水混合比减小而雨水混合比增加.

Based on eddy covariance (EC) measurements during 2016–20, the effects of sky conditions on the net ecosystem productivity (NEP) over a subtropical “floating blanket” wetland were investigated. Sky conditions were divided into overcast, cloudy, and sunny conditions. On the half-hourly timescale, the daytime NEP responded more rapidly to the changes in the total photosynthetic active radiation (PAR t ) under overcast and cloudy skies than that under sunny skies. The increase in the apparent quantum yield under overcast and cloudy conditions was the greatest in spring and the least in summer. Additionally, lower atmospheric vapor pressure deficit (VPD) and moderate air temperature were more conducive to enhancing the apparent quantum yield under cloudy skies. On the daily timescale, NEP and the gross primary production (GPP) were higher under cloudy or sunny conditions than those under overcast conditions across seasons. The daily NEP and GPP during the wet season peaked under cloudy skies. The daily ecosystem light use efficiency (LUE) and water use efficiency (WUE) during the wet season also changed with sky conditions and reached their maximum under overcast and cloudy skies, respectively. The diffuse photosynthetic active radiation (PAR d ) and air temperature were primarily responsible for the variation of daily NEP from half-hourly to monthly timescales, and the direct photosynthetic active radiation (PAR b ) had a secondary effect on NEP. Under sunny conditions, PAR b and air temperature were the dominant factors controlling daily NEP. While daily NEP was mainly controlled by PAR d under cloudy and overcast conditions.

利用NCEP再分析资料、常规及非常规气象观测资料,综合分析 2015 年 1月 9 日云南干季极端暴雨天气过程.结果表明:深厚的南支槽、低空切变线及地面冷锋共同作用导致此次过程;强位相热带季节内振荡(Madden-Julian Oscillation,MJO)处于"湿窗口"期,对水汽输送及对流发展有指示作用;南支槽前西南低空急流输送充沛水汽,暴雨落区与水汽强辐合区基本一致;高低空急流耦合,云南处于高空急流次级环流上升支,受锋面抬升,锋区次级环流上升支与高空急流次级环流上升支叠加,形成极强的上升运动;西南低空急流输送不稳定能量,滇西南暴雨区以强对流天气为主,滇中暴雨区以稳定性降水为主;结合稳定度参数的综合分析,有助于判断云南干季强对流天气落区.

利用2018年1月1日00时～2020年8月31日23时国家级多源融合逐时温度产品和国家级地面气象观测站逐时温度资料,针对平均误差、均方根误差、相关系数、时间误差等指标,对融合温度产品在云南的适用性进行评估.结果表明:融合产品小时温度平均误差介于?1～1℃,均方根误差在1.8℃以下,相关系数在0.95以上;融合产品极值温度在滇西北误差均较大,最高温在1～2月误差大,最低温在5～6月误差最大;极值温度出现时间和实况极值出现时间误差为0 h的占比,最高温和最低温分别是70％和73％;在时间不一致样本中,时间误差在2 h内的占比,最高温和最低温分别是86％和41％,最低温时间误差超过12 h的占40％.综合来看,融合温度产品在云南有较好的适用性,最高温的反演效果优于最低温.受降水、地形和海拔等因素的影响,融合温度产品在云南存在一定的系统性误差.

本文利用WRF(V3.9.1)模式中耦合Noah/SLUCM方案作为Control试验,研究了土地利用类型(Md04试验)、陆面过程(NoUCM试验)和湖泊(Nolake试验)对城市热岛强度及昆明城市气象要素水平、垂直的时空分布影响.主要结论如下:(1)四个试验城市热岛强度的平均日变化趋势相似,白天城市热岛强度较弱、夜间较强,在20时(北京时,下同)左右达到最大值.城市冠层(湖泊)对城市热岛有较明显的减(增)温,Control-NoUCM(Nolake)试验中,平均日最大差值为-0.79℃(+1.07℃).(2)从能量平衡方程分析Control-Md04试验,感热(潜热)通量的差值为+46.18(-79.71)Wm-2,潜热通量释放大于感热通量的绝对值.Control-NoUCM试验中,感热(潜热)通量的差值为-40.88(+29.60)Wm-2;因NoUCM试验未考虑几何建筑物储热与遮挡,太阳辐射大部分被地表所吸收,导致感热通量偏大.(3)四种试验中,15(07)时边界层高度达到最大(小)值.NoUCM(Nolake)试验中城市边界层高度分别降低103 m(32 m)左右,而Md04试验中城市边界层高度增加102 m左右.(4)湖泊(滇池)对城市热岛环流影响的试验表明,湖泊上空垂直运动较弱,但水平方向湖陆风较大,这有利于向城市输送水汽,增加干空气湿度,使城市中空气的水汽含量增加,同时增大潜热能量释放,降低感热通量,减小了垂直温度梯度.

Beihai wetland is a special type of alpine marsh in the southeast of the Qinghai-Tibet Plateau, with plants like a blanket floating on the water surface permanently. Long-term datasets with eddy covariance (EC) technique of evapotranspiration (ET) from the wetland ecosystem are still not too much. Based on EC measurements from 2016 to 2020, we investigated the variations of ET and its controlling factors over the Beihai wetland. Our results showed that ET was mostly influenced by the net radiation (Rn) from half-hourly to monthly timescales as a result of sufficient water supply at the observation site. In addition, the cloudiness was also a key factor con-trolling ET on daily scale by regulating radiation. On overcast and cloudy days, cloudiness suppressed ET primarily due to the decrease in the direct radiation (R-dir). While under sunny conditions, the increased diffuse radiation (R-dif) by cloudiness was conductive to increasing the canopy conductance (G(s)) and therefore ET. On annual scale, the annual ET ranged from 762.3 to 990.5 mm, and the annual precipitation was 1,210.4-1,780.2 mm during 2016-2020. The annual ET changed by around 30 %, while the annual precipitation changed by 47 %. There was a significant negative relationship between the annual ET and the annual precipitation. More annual precipitation in 2016 with more precipitation days and greater precipitation intensity than that in other four years resulted in less annual ET. Furthermore, the fraction of water surface was another factor controlling year-to-year variation of ET. There was a larger fraction of water cover in current site (37.3-38.4 % in 2017-2020) than that in the original site (29.7 % in 2016). Annual ET tended to increase as the fraction of water cover increased.

Ecosystem carbon balance might be affected by the variability of seasonal distribution of precipitation under global climate change. Using the eddy covariance (EC) technique, long-term observations of ecosystem net CO2 exchange (NEE) were acquired over Lijiang alpine meadow in the southeastern Tibetan Plateau from January 2014 to August 2019. During the wet season (from June to October), Lijiang meadow functioned as a carbon sink (− 37.6 ± 22.5 g C m−2 month−1), while in dry season, the meadow varied between a weak carbon source and sink with an average monthly NEE of − 3.9 ± 11.9 g C m−2 month−1. Monthly CO2 fluxes were mainly controlled by air temperature and soil water content. A large annual variation of CO2 uptake was observed. The annual NEE was − 140.3 g C m−2 year−1 in 2014 while − 247.0 g C m−2 year−1 in 2016. Correspondingly, the precipitation in wet season accounted 90% of annual precipitation in 2014 and 74% of that in 2016 despite the annual precipitation was larger than 1200 mm in both years. More precipitation in dry season can lead to longer period of net CO2 uptake, while more precipitation concentrated in wet season depressed the meadow’s light response through the decrease of the magnitude of light-saturated net CO2 exchange (NEEsat) at the onset and the end of growing season.

. Based on eddy covariance (EC) measurements from 2016 to 2020, the impact of sky conditions on net ecosystem 10 productivity (NEP) over Beihai wetland was examined. Sky conditions were classified into sunny, cloudy and overcast skies. On half-hourly timescale, the daytime NEP responds to the changing total photosynthetically active radiation (PAR t ) more efficiently under cloudy and overcast conditions than sunny conditions across seasons. Compared with sunny conditions, the apparent quantum yield (α) under overcast (cloudy) conditions increased 342.9% (271.4%) in spring, 17.6% (20.6%) in summer, 280.0% (230.0%) in autumn and 125.0% (25.0%) in winter, respectively. Unlike the patterns of half-hourly NEP, the 15 daily NEP was significantly lower under overcast conditions than that under cloudy and sunny conditions. And the daily NEP peaked under cloudy skies when the clearness index (CI) fluctuated around 0.3-0.6. Additionally, the ecosystem light use efficiency (LUE) and water use efficiency (WUE) also changed with the variations in sky conditions. The daily LUE and WUE reached their maximum values under overcast (CI: 0-0.2) and cloudy conditions (CI: 0.2-0.4), respectively. NEP was mainly controlled by the diffuse photosynthetically active radiation (PAR d ) and air temperature (Ta), and the direct photosynthetically 20 active radiation (PAR b ) had a secondary effect on NEP from to Path variations of NEP on half-hourly, daily and monthly timescale, meanwhile, the relative contribution of Ta to NEP varied considerably across different timescales, ranging from 18.4% (half-hourly timescales) to 50.3% (monthly timescales). The increase in VPD inhibited NEP, and 1.9%-16.8% of the variation of NEP explicated by from half-hourly to monthly timescales.

基于观测和ERA-Interim再分析资料,对2018年8月3—4日云南发生的连续性强降水过程进行诊断分析,发现:强降水发生前,云南位于两高(滇缅高压和位于南海地区的高压)之间的辐合区,台风及青藏高原东侧低涡对两高之间辐合区的正相对涡度输送,促使两高之间辐合区形成低涡;低涡在向南向西移动过程中,其中心自下而上保持西北—东南向倾斜;雨带随低涡切变移动,降水中心和低涡中心基本保持一致;在低层辐合、高层辐散的配置下,强降水中心出现在θse大值区,且与强上升运动大值区相一致;过程期间,云南为净水汽收入,东边界在整个过程中保持水汽收入,西边界和南边界水汽收支则随着低涡的移动在整个过程中出现输入输出反向变化.

本文利用中尺度模式WRF(weather research and forecasting)模拟了2016年干季和湿季高黎贡山南段(腾冲—保山地区)山谷风环流,分析YSU、MYJ、MYNN3、ACM2和BouLac五种边界层参数化方案在高黎贡山复杂下垫面的适用性.研究结果表明YSU方案对温度模拟的效果最好;ACM2模拟的风速平均绝对误差最小;MYNN3方案模拟的风向绝对误差最小,YSU方案和MYJ方案模拟的风向日变化趋势与观测更加一致.高黎贡山南段地区上午09时(北京时,下同)出现谷风环流,夜间19时转为山风环流.白天多为偏南风,夜间为偏北风和偏西风.白天山顶气流辐合而山谷气流辐散,夜间相反.白天风速大于夜间.干季西风风力较弱,有利于低层局地环流的发展;而湿季受较强的偏东背景风影响时,局地环流的发展受到抑制,边界层高度也就低于干季.干季西风遇到高黎贡山,在西坡下沉并形成涡旋,西侧湍流混合充分,边界层高度高;湿季偏东风使高黎贡山西侧谷风减弱,腾冲与保山的边界层高度相差不大.

Large uncertainties exist in carbon sequestration and water exchange process in wetland ecosystems under climate change. Beihai wetland is a very rare special type of alpine marsh with plants floating on the water surface located in the southeast margin area of the Tibetan Plateau. Based on the eddy covariance measurements from July 2015 to December 2016 over Baihai wetland, we have investigated the patterns of energy and carbon dioxide fluxes between the air and the alpine marsh and their main drivers. The latent heat flux (LE) was the main consumer of available radiation which accounted for 63% of net radiation (R-n) in 2016. R-n was the main factor determining H at both wet and dry season. Air temperature (T-a) and vapor pressure deficit (VPD)were most influenced with half-hourly LE during both wet and dry season, and VPD showed a larger influence on NEE in dry season than that in wet season. The total evapotranspiration (ET) in wet season occupied 60% of annual ET with an amount of 762.3 mm yr(-1) in 2016, which was much lower than the annual total precipitation (1780.2 mm yr(-1)). Photosynthetic active radiation (PAR) was the main controller in the half-hourly net ecosystem exchange (NEE), while T-a mainly controlled the seasonal variations in NEE. The annual total NEE, gross primary production (GPP) and ecosystem respiration (RE) were -233.8, 796.6 and 562.8 g C m(-2) yr(-1) in 2016. The fraction of vegetation to water surface changed from 66% to 74% in the study period. A positive linearly relationship was both found between the fraction of vegetation to water surface and CO2 uptake and evapotrans-piration. The fraction of vegetation to water surface could explain 40% variation of ET and 62% variation of NEE, respectively.

In mountainous lake areas, lake-land and mountain-valley breezes interact with each other, leading to an “extended lake breeze”. These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin, southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux (Hs) and carbon dioxide flux ( F_CO_2 ) and increases the latent heat flux (LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases F_CO_2 . For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases F_CO_2 . Results indicate that lakes in mountainous areas promote latent heat mixing but suppress carbon dioxide exchange.

利用云南省2325个国家级台站和区域自动观测站逐小时降水数据,分析了2014～2018年云南雨季和干季的降水量、降水频次和降水强度的空间分布特征以及关键区域的降水日变化演变特征.结果表明:受复杂地形影响,云南不同区域降水特征差异显著,且与我国东部地区显著不同.年均降水量大体呈西南高、西北低的分布特征.对于云南西北部的怒江河谷地区,干、雨季降水均为夜间峰值,降水频次高,但强度较弱.对于云南最西部(99°E以西)的保山德宏地区,该地区累计降水量为云南最大,这一区域各台站日变化峰值均较为一致地出现在上午,在陆地地区较为少见.相邻的普洱和元江河谷位于云南南部(23°N以南),雨季两区域降水相当,但元江河谷在干季与雨季均为突出的夜间至清晨降水峰值,普洱地区雨季则是明显的午后降水峰值.云南中部地区降水量较周边地区明显偏小,该地区降水频次在雨季主要表现为清晨峰值,而在干季却是午后峰值更为突出,这也与我国东部地区降水日变化特征差异明显.

Due to its special observation principle, GPS remote sensing atmospheric precipitation has the advantages of high time resolution and no weather conditions, and has been widely used in the research field of atmospheric precipitation. Using ground-based GPS precipitate water vapor data (GPS-PWV) and radiosonde-precipitate water vapor data (RS-PWV) that integrated by Radiosonde data, the error between GPS-PWV and RS-PWV in Tengchong is analyzed on its distribution of wet and dry seasons, also the difference between 00:00 UTC and 12:00 UTC. Results show that the RMSE of GPS-PWV and RS-PWV on both 00:00 UTC and 12:00 UTC are less than 5 mm, they correspond with each other well and their correlation coefficient is above 0.95, additionally, GPS-PWV value is stable than RS-PWV value. On the whole, the value of GPS-PWV is slightly larger than RS-PWV. And the mean absolute error between them has higher values, 4.5 mm in 2011 and 4.7 mm in 2012 from May to October (local rainy season) and lower values, 2.8 mm in 2011 and 3.1 mm in 2012 in November to April (local dry season). Besides, the mean absolute error in the morning seems has a difference with its component in the evening. Specifically, it is bigger on 12:00 UTC than on 00:00 UTC and the mean absolute errors on 12:00 UTC of two years are 27% and 11% larger than errors on 00:00 UTC respectively. The correlation of mean absolute error and surface vapor pressure, surface air temperature is examined in this study as well. We achieved that the correlation coefficient between mean absolute error and surface vapor pressure, surface air temperature equals 0.32, 0.37 separately. Diverse characters of mean absolute error under different precipitation conditions are also discussed. The outcome is that the mean absolute error has a higher value on rainy days and a lower value on clear days. However, during the precipitation periods, it appears that the mean absolute error and the rainfall situation don’t agree with each other well, it is likely to change randomly.

利用1998-2013年TRMM卫星上携带的闪电探测仪(LIS)监测的闪电资料以及云南6个气象站降水观测资料,分析云南闪电活动的时空分布特征及其与降水量的关系.结果 表明:(1)云南地区平均闪电密度为4.7fl·km-2·a-1,闪电密度分布与地形密切相关,自西北向东南呈“V”字型带状增大,滇南的西双版纳、普洱东南部和中越边境的闪电活动最为活跃,最高值为30.6 fl·km-2·a-1.(2)闪电活动具有明显的季节变化和日变化.春、夏季闪电活动明显多于秋、冬季,其中春季闪电活动主要发生在滇南,而夏季则在滇东.滇北闪电活动的月分布呈单峰型,峰值在7月或8月,且闪电密度与降水量有较好的相关性,而滇西、滇南和滇东南则呈双峰型,峰值在4月,次峰值在7月或8月,闪电密度与降水量的相关性较差.云南大部地区闪电易发生在当地时间16:00-20:00,而密度高值区的闪电活动多发生在夜间.(3)云南闪电活动明显受地形和海拔高度影响,且与季风密切相关.

The differences in planetary boundary layer characteristics, in particular atmospheric boundary layer height (ABLH), humidity, and local circulations in pre-monsoon and monsoon period over the Erhai Lake, were simulated by the lake-atmosphere coupled model WRF v3.7.1. No lake simulations were also conducted to investigate lake effects over complex topography. During pre-monsoon period, local circulation was fully developed under weak synoptic system. The ABLH ran up to 2300 m or so. During monsoon period, temperature difference between land and lake became smaller, resulting in weaker local circulations. The height of circulation reduced by 500 m, and ABLH ran up to 1100 m during the day. Enhanced soil moisture and low surface temperature due to monsoon rainfalls in July could be the main reason for the slightly lower ABLH over the Erhai Lake area. Specific humidity of the boundary layer increased 8.8 g kg−1 or so during monsoon period. The Erhai Lake enlarged thermal contrast between valley and mountain slope in the Dali Basin. The lake reduced air temperature by 2~3 °C during daytime and increased air temperature by nearly 2 °C in the evening. Due to its small roughness length and large thermal capacity, the Erhai Lake enlarged lake-land temperature difference and local wind speed. A cyclonic circulation was maintained by the combination of mountain breeze and land breeze in the south of the lake. The lake decreased air temperature, increased specific humidity, and reduced ABLH during daytime, whereas the opposite effect is presented at night.

利用2001-2017年云南省气象局收集的雷灾资料进行统计分析,给出了云南省有人员伤亡的雷电灾情特征.资料包括雷灾造成了728人死亡和949人受伤,平均每年有42.3人死于雷灾和55.3人在雷灾中受伤.在云南省每年每一百万人中有0.99人死于雷击和1.7人在雷灾中受伤.云南省雷灾伤亡多发生在东部和南部地区,西部相对较少.红河最为严重,总计雷灾造成107人死亡,127人受伤;当考虑人口权重时西双版纳雷灾人员死伤率最高.云南雷灾伤亡主要发生在5-8月,占全年的82％以上,8月最高.人员伤亡的雷灾主要发生在13:00-20:00,占73％,16:00为峰顶.雷灾中受伤害的农民占总死伤人数的97％,城市人员仅占3％.雷灾中男性占伤亡人数的57％,在雷灾伤亡人员年龄分布中,40～49岁这一年龄段最多.统计人员伤亡雷灾中的雷击地点,最多的发生在农田,为39％,其次为树下,为17％,以下依次为开阔地和放牧等.

两种类型冷却屋顶(高反照率屋顶、绿色屋顶)的研究对于北京夏季城市高温的缓解作用具有重要的意义.耦合单层城市冠层模式(SLUCM)与天气研究与预报(WRF3.8)模式,采用北京市及其外围地区158个站点气象资料评估模式对照案例(case1)的模拟性能,并选取7组不同反照率屋顶案例(case2-4)和不同覆盖比例的绿色屋顶案例(case5-8)进行敏感性试验.研究结果表明:(1)在北京城市区域,高反照率为0.85的屋顶(case4)比绿色占比100％的屋顶(case8)具有更好的降温效果,case4的3d平均降温可达到0.90℃,而case8降温为0.46℃.(2)屋顶反照率每增加0.1,会导致北京城市区域最高气温降低0.27℃;绿色屋顶比例的增大也会导致温度的降低,每增加10％,最高气温降低0.16℃.(3)两种冷却屋顶对城市热岛也存在显著的影响,在13 14时(北京时),case4与case1对比的城市热岛(UHI)降温最大差值为1.47 ℃,比case8的城市热岛降温更加明显.(4)在城市区域垂直高度上,冷却屋顶的降温作用可达到1.2 km,同时湍流运动存在明显的减弱;在3d的12 18时,case4、case8与case1对比,边界层高度平均降低了669与430 m.