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The stratification of the atmospheric surface layer (ASL) plays an important role in regulating the water vapor and heat exchange across the lake–air interface. Based on one year of data measured by the eddy covariance technique over Erhai Lake in 2015, the ASL stability ($${\rm{\zeta }}$$) was divided into six ranges, including unstable ($$ - 1 \le {\rm{\zeta }} \lt - 0.1$$), weakly unstable ($$ - 0.1 \le {\rm{\zeta }} \lt - 0.01$$), near-neutral1 ($$ - 0.01 \le {\rm{\zeta }} \lt 0$$), near-neutral2 ($$0 \le {\rm{\zeta }} \lt 0.01$$), weakly stable ($$0.01 \le {\rm{\zeta }} \lt 0.1$$), and stable ($$0.1 \le {\rm{\zeta }} \lt 1$$). The characteristics of ASL stability conditions and factors controlling the latent ($$\rm LE$$) and sensible heat ($$H$$) fluxes under different stability conditions were analyzed in this study. The stability conditions of Erhai Lake have noticeably seasonal and diurnal variation, with the near-neutral and (weakly) stable stratification usually occurring before July, with frequencies of 51.7% and 23.3%, respectively, but most of the (weakly) unstable stratification was observed after July, with a frequency of 59.8%. Large evaporation occurred even in stable atmospheric conditions, due to the coupled effects of the relatively larger lake–air vapor pressure difference and wind speed. The relative controls of $$\rm LE$$ and $$H$$ by different atmospheric variables are largely dependent on the stability conditions. In stable and unstable ranges, $$\rm LE$$ is closely correlated with the vapor pressure difference, whereas in weakly unstable to weakly stable ranges, it is primarily controlled by wind speed. $$H$$ is related to wind speed and the lake–air temperature difference under stable conditions, but shows no obvious relationship under unstable conditions.

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 (Rn) in 2016. Rn was the main factor determining H at both wet and dry season. Air temperature (Ta) 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 Ta 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 evapotranspiration. The fraction of vegetation to water surface could explain 40% variation of ET and 62% variation of NEE, respectively.

Based on five years of eddy covariance measurements at multiple levels (47, 140, and 280 m) of Beijing's 325-m meteorological tower, the exchange process of CO2 fluxes between the atmosphere and urban surface were investigated. As a result of the total vehicle control policy from 2011 in Beijing, the growth rate of annual total CO2 flux at 140 m is 7.8% from 2008–2010 but 2.3% from 2010–2012. With the minimum vegetation cover and largest population density, the 5-yr average annual total CO2 flux at 140 m is largest (6.41 kg C m−2 yr−1), compared with that at 47 m (5.78 kg C m−2 yr−1) and 280 m (3.99 kg C m−2 yr−1). With regards to annual total CO2 fluxes in Beijing, vehicle numbers and population are the main controlling factors. The measured CO2 fluxes were highly dependent on land cover/use in the prevailing wind direction. The CO2 fluxes at three layers all correlated positively with road fraction, with the R2 values being 0.69, 0.57, and 0.54 (P 摘要 本文基于北京325米气象塔在47, 140, 和280米三层高度的5年涡动相关观测资料, 研究了城市下垫面与大气间的CO2交换过程.由于北京市2011年开始实行工作日汽车尾号限行, 140米高度CO2通量的年增长率由2008–2010年的7.8%降低到2010–2012年的2.3%.140米高度通量源区内植被比例最小且人口密度最大, 因此140米高度的5年平均CO2通量年总量)6.41 kg C m−2 yr−1(大于47米)5.78 kg C m−2 yr−1(和280米)3.99 kg C m−2 yr−1(.在年尺度上, 北京汽车总保有量和总人口是最重要的CO2通量控制因子.CO2通量随风向的变化主要与风向对应的通量源区内下垫面土地利用方式有关.三层高度的夏季CO2通量均与道路的比例呈正相关关系.47, 140, 和280米的决定系数分别为0.69, 0.57, 和0.54 (P

Uncertainties in satellite rainfall estimation may derive from both the local rainfall characteristics and its subpixel variability. To study this issue, Micro Rain Radars and a rain gauge network were deployed within a 9-km satellite pixel in the semi-arid Xilingol grassland of China in summer 2009. The authors characterized the subpixel variability with the coefficient of variation (CV) and evaluated the satellite rainfall estimation for this semi-arid area. The results showed that rainfall events with a high CV were mostly convective with a small amount of rainfall. Spatially inhomogeneous rainfall was most likely to occur at the edges of small clouds producing rain. The performance of the TRMM (Tropical Rainfall Measuring Mission) 3B42V7 product for daily rainfall was better than that of the CMORPH (Climate Prediction Center morphing technique) and PERSIANN (Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks) products, although the TRMM product tended to overestimate rainfall in a lake area of the semi-arid grassland. 摘要 卫星估雨精度的不确定性受到当地降雨类型和像元内降雨非均匀性影响, 而结合这两个关键因素开展半干旱草原卫星估雨的研究有限. 2009年夏, 我们在中国锡林郭勒半干旱草原用多部微雨雷达和雨量计构建了9 km卫星像元降雨观测网, 观测了像元内降雨非均匀性(空间变异系数CV), 并评估了卫星估雨精度. 结果表明: (1) CV值受像元内平均降雨量, 降雨类型, 降雨云面积及移向等影响, 如高CV值的降雨过程大多为平均降雨量小, 对流性降雨过程, 降雨云边缘像元CV值较高; (2) TRMM 3B42V7 卫星估雨产品适用性较好, CMORPH和PERSIANN次之, 但TRMM 3B42V7易在半干旱草原湖泊处高估降雨.

Vertical raindrop size distributions of two stratiform rain events were measured with a Micro Rain Radar during summer 2009 at a semiarid continental site located in Xilinhot, China (43°38′N, 116°42′E). The sequential intensity filtering technique (SIFT) was used to minimize the effect of the spurious variability on disdrometric data to obtain the reflectivity–rain rate (Z–R) relationship (Z = aRb). Compared with the least squares regression (LSR) method, SIFT led to a −5% to 4% change in the coefficient (a) and an 8%–15% increase in the exponent (b) of the Z–R relationship at 300 m. Rainfall estimation using the Z–R relationship with SIFT had lower standard deviation than that with LSR. The vertical variability of the mean rain rate, total raindrop numbers, and parameters (a and b) of the Z–R relationship was small below a melting layer, suggesting that using the radar reflectivity of weather radar to estimate stratiform rainfall is relatively accurate, at least in the Xilinhot area.

The effects of precipitation pulses on evapotranspiration (ET) and CO 2 fluxes were evaluated over different land surfaces in a semiarid area using eddy covariance technique. ET responded to rain events throughout the growing season, but the degree of responses varied among seasons. In spring and fall, ET slightly responded to precipitation pulses, because the precipitation amount in the rainfall event was small and very discrete. As the rainy season started in early summer, responses of ET to precipitation pulses significantly increased. In late summer, the intensity of responses in ET was weakened because the soils retain moisture by the high-frequency rainfall events and the antecedent soil moisture. Regarding CO 2 exchange, in early summer, the net CO 2 uptake slightly increased at the cultivated corn site after rain pulses, while the degraded grassland site experienced comparatively greater responses. In late summer, the cultivated corn site exhibited more negative CO 2 flux after rain than the grassland site, and the responses of net CO 2 uptake to rain pulses were much stronger than those in early summer. The soil moisture content and vegetation cover are the key factors in determining the responses of ET and CO 2 fluxes to precipitation pulses in these two semiarid ecosystems.

Based on the long-term trends analysis of five meteorological parameters (temperature, precipitation, wind speed, sunshine duration and relative humidity) in the four chosen stations of different settings, this paper attempts to reveal the characteristics of climate change in Urumqi City during 1960–2013. Our analytical results showed that both the temperature and precipitation in the Urumqi City have increased significantly since the middle 1980s. Autumn was the season when the temperature increased most drastically, and winter was the season when the precipitation increased most drastically. The average minimum temperature increased faster than the average maximum temperature, thus resulting in greatly reduced diurnal and annual temperature ranges. The wind speed was weakening significantly since the middle 1980s. The sunshine duration did not display any geographic coherence or consistency among different stations. The relative humidity has maintained more or less a constant, meaning that the absolute amount of water vapor has been increased under warming conditions. Comparatively, the Urumqi station (i.e., the urbanized area) had the most pronounced changes in temperature, precipitation and sunshine duration and the most pronounced changes were possibly due to the combined effects of natural and anthropogenic factors. Climate change in the mountainous area was synchronous with that in the plain area and the underlying surfaces and topographies, together with degrees of human activities, distinguished the regional climatic responses to global warming.

Phenology plays an important role in the carbon exchange process. Seven years of continuous eddy covariance data across two different ecosystems in a semiarid area were used to investigate the variation in phenology indices, its effect on the carbon exchange process, and responses to climate change. The results showed that there was large annual variation for vegetation phenology. The GSL (growing season length) displayed an obvious increasing trend for the grassland ecosystem during the 7 years, and it was most determined by SOS (the start day of growing season). The growing season was divided into three periods, the recovery period (S1), the stable period (S2), and the senescence period (S3). Both ecosystems had a similar ratio of Re (ecosystem respiration) to GPP (gross primary production) during S1 and S2 periods but a much larger Re/GPP ratio during the last growing period. The inter-annual variation of the peak rate was most responsible for the NEP (net ecosystem production) and its components (GPP and Re) in both ecosystems. The inter-annual variation of recovery rate, GSL and SOS was found to be closely correlated to Re for the grassland ecosystem, while that could not be found for the cropland ecosystem. The temperature in June was most closely correlated with the peak rate of GPP and NEP for grassland ecosystem, with a significant correlation coefficient of −0.90 and −0.82, respectively. Meanwhile, the precipitation in July was found to be closely correlated with GPP for both ecosystems, with a similar correlation coefficient of 0.83. The precipitation and temperature roughly exhibited an inverse effect on vegetation phenology in this semiarid area. The variation of temperature in the early month and precipitation in mid growing season showed a more significant effect on main phenology indicators for the cropland ecosystem than those for grassland ecosystem.

The planetary boundary layer (PBL) parameterization schemes play a critical role in the weather and climate models, while they describe physical processes associated with the momentum, heat and humidity exchange between land surface and atmosphere. The sensitivity of boundary layer variables to eight PBL parameterization schemes (three non-local and five local closure schemes), available in the Weather Research and Forecasting (WRF) model, is evaluated over the central Tibetan Plateau with field measurements of the Third Tibetan Plateau atmospheric scientific experiment (TIPEX III) in July. Model results showed acceptable behavior, but no particular scheme produced the best performances for all observation stations and meteorological parameters. All PBL schemes underestimated the surface temperature over the central Tibetan Plateau. The BouLac scheme showed the minimum cold bias of the surface temperature. For the surface energy budget components, it was found that the sensible heat flux and the downward longwave radiation were the main factors causing the lower surface temperature. The sub-grid scale gravity wave drag was added to reduce biases result from unresolved topography over the central Tibetan Plateau. It led to smaller cold bias, causing warmer lower-tropospheric temperature, smaller water vapor content and higher PBL height. The modified model results show more close to the observation.

The eddy covariance technique was used to measure evapotranspiration (ET) at four different grazing intensity sites to investigate the grazing effects on ET in the semiarid steppe ecosystems of Inner Mongolia. By reducing available energy, and decreasing soil water content (SWC), grazing decreased ET on a seasonal scale compared with the site ungrazed since 1979 (UG79). The most important climatic factor controlling ET on daily scale shifted from SWC to Net radiation (Rn) when grazing intensity increased. SWC, Rn and air temperature (or vapor pressure deficit) can explain 59%–71% of the variation in daily ET. On the other hand, leaf area index (LAI) affected ET slightly at UG79 under the commonly limited soil water conditions. Even no effect of LAI at the heavily grazed site was detected. This suggests that the direct effect of grazing reducing LAI on ET is not significant in this semiarid steppe ecosystem. Soil evaporation compensates for most of the loss in transpiration due to reduced LAI.

Several studies have been selected to review water tank modeling of the atmospheric boundary layer (ABL) and demonstrate that water tank simulations have been a key factor in developing scientific knowledge and promoting further research of the ABL. The areas discussed include similarity analysis of modeling, basic dispersion processes, characteristics of the convective boundary layer (CBL), parameterizations of the entrainment zone (EZ), the characteristics of turbulence in the CBL, and the influence of plain-valley terrain and other inhomogeneities on atmospheric boundary layer structure. Technical values of some parameters are noted and potential improvements in water tank modeling based on continuing advances in new technology are also discussed. The limitations of water tank models for characteristics of the CBL and possible solutions to their limitations are briefly discussed.

Serine carboxypeptidase-like proteins (SCPLs) comprise a large family of protein hydrolyzing enzymes that play roles in multiple cellular processes. During the course of study aimed at elucidating the molecular basis of induced immunity in rice, a gene, OsBISCPL1, encoding a putative SCPL, was isolated and identified. OsBISCPL1 contains a conserved peptidase S10 domain, serine active site and a signal peptide at N-terminus. OsBISCPL1 is expressed ubiquitously in rice, including roots, stems, leaves and spikes. Expression of OsBISCPL1 in leaves was significantly up-regulated after treatments with benzothiadiazole, salicylic acid, jasmonic acid and 1-amino cyclopropane-1-carboxylic acid, and also up-regulated in incompatible interactions between rice and the blast fungus, Magnaporthe grisea. Transgenic Arabidopsis plants with constitutive expression of OsBISCPL1 were generated and disease resistance assays indicated that the OsBISCPL1-overexpressing plants showed an enhanced disease resistance against Pseudomonas syringae pv. tomato and Alternaria brassicicola. Expression levels of defense-related genes, e.g. PR1, PR2, PR5 and PDF1.2, were constitutively up-regulated in transgenic plants as compared with those in wild-type plants. Furthermore, the OsBISCPL1-overexpressing plants also showed an increased tolerance to oxidative stress and up-regulated expression of oxidative stress-related genes. The results suggest that the OsBISCPL1 may be involved in regulation of defense responses against pathogen infection and oxidative stress.

Summary To study the effect of land use change from marshland to croplands (rice and soybean cultivation), the water and energy fluxes in marshland, rice and soybeans were measured in northeastern China by the eddy covariance method for two growing seasons (May–October in 2005 and 2006). The rice (flooded until early September) and soybean (dry land) croplands were reclaimed from marshlands over 15 years ago. The annual precipitation in 2005 (480 mm) was below the 1981–2004 average (564 ± 130 mm), the precipitation in 2006 (655 mm) was significantly above average. The conversion of marshland to rice cropland resulted in an enhancement in latent heat flux (LE) and a decrease in sensible heat flux (H), which caused an increase in the ratio of LE and net radiation (LE/Rn) from 0.6 to 0.8 on average, and a decrease in H/Rn from 0.4 to 0.2 on average for the growing season. However, where the marshland was converted to soybean cropland, the latent heat flux was lower in 2005 under dry conditions, but higher in 2006 under wet conditions than it had been previously been, which was the opposite of the trend of H. Therefore, LE/Rn for soybean dropped to about 0.2 in the dry month of June 2005, and rose to 0.7 in the wet month of June 2006. H/Rn for soybeans shows opposite variation in LE/Rn in both years. The maximum evapotranspiration (ET) was about 4.5, 6–7 and 5 mm day−1 for marshland, rice and soybeans, respectively. Rn, air temperature (Ta), vapor pressure deficit (VPD) and leaf area index (LAI) were important environmental and biological factors controlling the seasonal dynamics of LE and H for the three ecosystems, which explains about 80% of LE and 50% of H for marshland and rice; and 30–50% of LE and 60% of H for soybeans. Among them, Rn was the primary variable controlling the variations of LE and H for marshland and rice. However, for soybeans, VPD played a more important role in LE under dry conditions.

Observational analyses and numerical simulations were carried out to study the characteristics of the winter urban boundary layer of a large city. The observations showed that with light winds the ground inversion at nighttime in urban areas was about 200 m deep. The heat island circulation, caused mainly by anthropogenic heating, induced reverse flow at the downwind part of the city. A shallow internal boundary layer with a depth of 50–80 m developed from the fringe of the city. In the daytime heavy smoke attenuated the solar radiation, and caused a cold island in the urban area, and retarded the development of a convective boundary layer. The features described above were well simulated by the numerical model.