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The Surface Urban Energy and Water Balance Scheme (SUEWS) has recently been introduced to include a bottomup approach to modelling carbon dioxide (CO2) emissions and sink in urban areas. In this study, SUEWS is evaluated against radiation flux observations and eddy covariance (EC) measured turbulent fluxes of sensible heat (QH), latent heat (QE), and CO2 (FC) at a densely built neighborhood in Beijing. The model sensitivity to maximum conductance (gmax) and leaf area index (LAI) is examined. Site-specific gmax is obtained from observations over local vegetation species, and LAI parameters by optimization with remotely sensed LAI obtained from a MODIS/Terra data product. For simulation of anthropogenic CO2 components, local traffic and population data are collected. In model evaluation, the mismatch between the measurement source area and simulation domain is also considered. Using the optimized gmax and LAI, the modelling of heat fluxes is noticeably improved, showing higher correlation with observations, lower bias, and more realistic seasonal dynamics of QE and QH. In comparison to heat fluxes, the FC module shows lower sensitivity to the choice of gmax and LAI. This can be explained by the low relative contribution of vegetation to net FC in the modelled area. SUEWS successfully reproduces the average diurnal cycle of FC and annual cumulative sums. Depending on the size of the simulation domain, the modelled annual accumulated FC ranges from 7.2 to 8.5 kg C m−2 yr−1, when compared to 7.5 kg C m−2 yr−1 observed by EC. Traffic is the dominant CO2 source, contributing 63–73 % to the annual total CO2 emissions, followed by human metabolism (14–18 %), respiration released by vegetation and soil (6–11 %) and building heating (6–9 %). Vegetation photosynthesis offsets only 4–8 % of the total CO2 emissions. We highlight the importance of choosing optimal LAI parameters and gmax when SUEWS is used to model surface fluxes. The FC module of SUEWS is a promising tool in quantifying urban CO2 emissions at the local scale, and therefore assisting to mitigate urban CO2 emissions.

The percolation thresholds of poly ether ether ketone/graphene (PEEK/Gr) composites in most studies are high due to the random distribution of Gr in the matrix. Here, aminated poly-ether-ether-ketone/graphene network (PEEK-NH2/GN) nanocomposites were prepared by electrostatic adsorption of PEEK-NH2 with positive charges and graphene oxide with negative charges, followed by in -situ reduction and hot-pressing. The GN structure of composites was well presented in the images of scanning electron microscope. The PEEK-NH2/GN nanocomposites exhibited excellent electrical conductivity with a maximum conductivity of 0.0634 S·cm−1 and a percolation threshold as low as 0.25 vol%. In addition, the maximum tensile strength of nanocomposites was reached at 93 MPa when the Gr content was 0.5 wt%. We believe that this approach is a new avenue for the production of low filler high conductive polymer composites with potential commercial prospects in various fields.

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 ( $$\boldsymbol{F}_{\text{CO}_{2}}$$ ) and increases the latent heat flux (LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases $$\boldsymbol{F}_{\text{CO}_{2}}$$ . For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases $$\boldsymbol{F}_{\text{CO}_{2}}$$ . Results indicate that lakes in mountainous areas promote latent heat mixing but suppress carbon dioxide exchange.

Based on eddy covariance (EC) measurements from 2016 to 2020, the impact of sky conditions on net ecosystem 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 (PARt) 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 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 (PARd) and air temperature (Ta), and the direct photosynthetically active radiation (PARb) had a secondary effect on NEP from half-hourly to monthly timescales. Path analysis revealed that PARb and Ta were the main controls affecting NEP under sunny conditions. While under cloudy and overcast conditions, PARd was the most responsible for the variations of NEP.

The effects of acid soaking as a pre-treatment on the glycoalkaloid and acrylamide levels in raw and cooked potatoes (French fries) were examined. Soaking raw potato cuts in 1.0%, 2.5% or 5.0% acetic acid solutions for at least 8 hours resulted in90% reduction of α-solanine and α-chaconine in potato samples. Processing of pre-acid soaked potato cuts into French fries resulted in an additional50% decrease in the glycoalkaloid contents in the samples. Soaking time was found to be a more important factor in reducing glycoalkaloid levels compared to the acid solution concentrations. Over a 95% reduction in acrylamide was also observed in potato cuts pre-soaked in acetic acid before cooking. The reduction in acrylamide formation in the pre-soaked French fry samples was attributed to the lowered pH and the removal of reducing sugars and asparagine in the raw samples prior to cooking. Findings in this study demonstrate that pre-treatment using acid soaking provides a simple and effective way to mitigate glycoalkaloid and acrylamide levels in potatoes.

The Tibetan Plateau (TP) is a key area affecting forecasts of weather and climate in China and occurrences of extreme weather and climate events over the world. The China Meteorological Administration, the National Natural Science Foundation of China, and the Chinese Academy of Sciences jointly initiated the Third Tibetan Plateau Atmospheric Science Experiment (TIPEX-III) in 2013, with an 8–10-yr implementation plan. Since its preliminary field measurements conducted in 2013, routine automatic sounding systems have been deployed at Shiquanhe, Gaize, and Shenzha stations in western TP, where no routine sounding observations were available previously. The observational networks for soil temperature and soil moisture in the central and western TP have also been established. Meanwhile, the plateau-scale and regional-scale boundary layer observations, cloud-precipitation microphysical observations with multiple radars and aircraft campaigns, and tropospheric-stratospheric air composition observations at multiple sites, were performed. The results so far show that the turbulent heat exchange coefficient and sensible heat flux are remarkably lower than the earlier estimations at grassland, meadow, and bare soil surfaces of the central and western TP. Climatologically, cumulus clouds over the main body of the TP might develop locally instead of originating from the cumulus clouds that propagate northward from South Asia. The TIPEX-III observations up to now also reveal diurnal variations, macro- and microphysical characteristics, and water-phase transition mechanisms, of cumulus clouds at Naqu station. Moreover, TIPEX-III related studies have proposed a maintenance mechanism responsible for the Asian “atmospheric water tower” and demonstrated the effects of the TP heating anomalies on African, Asian, and North American climates. Additionally, numerical modeling studies show that the Γ distribution of raindrop size is more suitable for depicting the TP raindrop characteristics compared to the M-P distribution, the overestimation of sensible heat flux can be reduced via modifying the heat transfer parameterization over the TP, and considering climatic signals in some key areas of the TP can improve the skill for rainfall forecast in the central and eastern parts of China. Furthermore, the TIPEX-III has been promoting the technology in processing surface observations, soundings, and radar observations, improving the quality of satellite retrieved soil moisture and atmospheric water vapor content products as well as high-resolution gauge-radar-satellite merged rainfall products, and facilitating the meteorological monitoring, forecasting, and data sharing operations.

Leptosphaeria maculans causes blackleg disease in Brassica napus. The blackleg disease is mainly controlled by resistance genes in B. napus. Previous studies have shown that the blackleg resistant BLMR2 locus that conferred horizontal resistance under field conditions, is located on chromosome A10 of B. napus. The purpose of this study is to fine map this locus and hence identify a candidate gene underlying horizontal resistance. The spectrum of resistance to L. maculans isolates of the resistance locus BLMR2 was analyzed using near isogenic lines, resistant, and susceptible cultivars. The results showed that this locus was horizontally resistant to all isolates tested. Sequence characterized amplified regions (SCAR), simple sequence repeats (SSR), and single nucleotide polymorphism (SNP) markers were developed in the chromosome region of BLMR2 and a fine genetic map was constructed. Two molecular markers narrowed BLMR2 in a 53.37 kb region where six genes were annotated. Among the six annotated genes, BnaA10g11280D/BnaA10g11290D encoding a cytochrome P450 protein were predicted as the candidate of BLMR2. Based on the profiling of pathogen induced transcriptome, three expressed genes in the six annotated genes were identified while only cytochrome P450 showed upregulation. The candidate corresponds to the gene involved in the indole glucosinolate biosynthesis pathway and plant basal defense in Arabidopsis thaliana. The molecular markers identified in this study will allow the quick incorporation of the BLMR2 allele in rapeseed cultivars to enhance blackleg resistance.

Wetlands are “hot spot” area of global climate change, which are obviously sensitive to climate change. Under climate change, the carbon sequestration potential and carbon balance over wetland ecosystems are greatly altered, and large uncertainties are still existed in carbon budgets over these areas. Tengchong Beihai wetland is the only highland “floating blanket” lake wetland which is located in Southwest of China. As this land surface is composed by both water and terrestrial land surface, it’s doubted whether this type of wetland behaves more like lake or the latter one. Based on one year continuous observation measured with eddy covariance technique over Beihai wetland and Erhai Lake in 2016, the patterns of CO2 flux and energy fluxes over Tengchong wetland and Erhai lake are analyzed. The results show the diurnal variation of H and LE are both similar to Rn, which is different with Erhai lake. Erhai lake has a higher evaporation rate even in nighttime, which is much larger than Beihai wetland, due to the “floating blanket” vegetation could obviously reduce the evaporation rate. Beihai wetland acts as CO2 sink for the most time of the year, with an annual CO2 flux of -202.2 g C m-2, while Erhai Lake acted as CO2 source with an annual CO2 flux of 143.7 g C m-2. The results indicate the carbon and water exchange process in Beihai wetland behaves more like vegetated land surface.

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

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.

Background: Neurotrophin receptor-interacting MAGE homolog (NRAGE) has been considered as a tumor suppressor. In the previous study, we established human esophageal carcinoma resistance cell line TE13R120 and found the difference of NRAGE expression between TE13 and TE13R120 cells by gene microarray. Herein, we further discuss the possible molecular mechanism of NRAGE on participating the radiation sensitivity of esophageal carcinoma cells. Materials and Methods: We used colony formation assay to measure the surviving fraction and relevant radiobiological parameters. NRAGE expression was estimated by immunofluorescence and Western blot. Tumor growth factor-β (TGF-β) was used for inducing epithelial–mesenchymal transition (EMT) in TE13 cells to detect the relationship between NRAGE and EMT; the capacity of cell migration was also assessed by wound healing assay. Results: TE13R120 cells were showed significantly radioresistance compared with TE13. The D0, Dq, and N value of TE13R120 were all higher than those of TE13 (2.499, 1.991, and 2.219 vs. 2.242, 0.854, and 1.645), as well as SF2 (0.734 vs. 0.538). Results of immunofluorescences showed that NRAGE was mainly expressed in the nucleus of TE13R120 cells, but in TE13 cells, it was mainly in cytoplasm. In addition, EMT phenotype was observed in TE13R120 cells and TGF-β-induced EMT in TE13 cells, E-cadherin expression was decreased, but vimentin was upregulated. Furthermore, TE13 cells have a rising tendency in NRAGE nucleus expression after treatment with TGF-β. Results of wound healing assay showed that the cell migration of TE13R120 and TGF-β-induced EMT in TE13 cells were remarkably enhanced. Conclusions: Our results indicate that NRAGE subcellular localization is related to radiation resistance of esophageal carcinoma cell and EMT may be involved in NRAGE subcellular location.

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.

Turbulence data (2008–2012) from a 325 m meteorological tower in Beijing, which consisted of three layers (47, 140, and 280 m), was used to analyze the vertical distribution characteristics of turbulent transfer over Beijing city according to similarity theory. The conclusions were as follows. (1) Normalized standard deviations of wind speeds σ i / u * were plotted as a function only of a local stability parameter. The values under near-neutral conditions were 2.15, 1.61, and 1.19 at 47 m, 2.39, 1.75, and 1.21 at 140 m, and 2.51, 1.77, and 1.30 at 280 m, showing a clear increase with height. The normalized standard deviation of wind components fitted the 1/3 law under unstable stratification conditions and decreased with height under both stable and unstable conditions. (2) The normalized standard deviation of temperature fitted the ‒1/3 law in the free convection limit, but was quite scattered with different characteristics under near-neutral conditions. The normalized standard deviations of humidity and the CO2 concentration fitted the ‒1/3 law under unstable conditions, and remained constant under near-neutral and stable stratification. The normalized standard deviation of scalars, i.e., temperature, humidity, and CO2 concentration, all increased with height. (3) Compared with momentum, and the water vapor and CO2 concentrations, the turbulence correlation coefficient for heat was smaller under near-neutral conditions, but larger under both stable and unstable conditions. A dissimilarity between heat, and the water vapor and CO2 concentrations was observed in urban areas. The relative correlation coefficients between heat and each of momentum, humidity, and CO2 concentration (| r wT / r uw |, | r wT / r wc | and | r wT / r uq |) in the lower layers were always larger than in higher layers, except for the relative correlation coefficient between heat and humidity in an unstable stratification. Therefore, the ratio between heat and each of momentum, humidity, and CO2 concentration decreased with height.

Tropical cyclones and meiyu-baiu fronts, as the two main synoptic systems over East Asia, bring heavy rain during summers, but their long-term and vertical raindrop size distribution (RSD) features over the midlatitude Japan Islands are limited. Radar-based quantitative precipitation estimation (QPE) techniques require RSD observations. In this study, five-year observations from Tokyo with a ground-based impact Joss-Waldvogel disdrometer (JWD) and a vertically pointing micro rain radar (MRR) with a vertical range of 0.2&ndash, 6.0 km were used to study the vertical structures of RSD and QPE parameters. The results showed that the convective rain associated with tropical cyclones had a maritime nature, while the rain associated with the meiyu-baiu front had a continental nature. The rain associated with tropical cyclones had a relatively higher concentration of raindrops and a larger average raindrop diameter than the rain associated with the meiyu-baiu front. The Z&ndash, R (radar reflectivity-rain rate) relationships (Z = ARb) based on the JWD data for tropical cyclones, the meiyu-baiu front and total summer rainfall in Tokyo were Z = 189 R1.38, Z = 214 R1.35 and Z = 212 R1.33, respectively. When the Z&ndash, R relationships obtained in this study were used to replace the operational relationship of Z = 300 R1.4, the standard deviation of the rain rate was reduced from 5.50 mm/h (2.34 mm/h) to 2.34 mm/h (1.32 mm/h) for typhoon (meiyu-baiu front) rainfall, although the change for total summer rainfall was small. In addition, with increasing height below 4 km, the value of A and b decreased.

Based on eddy covariance flux data from July 15, 2014, to December 31, 2015, the water and CO2 fluxes were compared over a semiarid alpine steppe (Bange, Tibetan Plateau) and a humid alpine meadow (Lijiang, Yunnan) on the Tibetan Plateau and its surrounding region. During the wet season, the evaporative fraction (EF) was strongly and linearly correlated with the soil water content (SWC) at Bange because of its sparse green grass cover. In contrast, the correlation between the EF at Lijiang and the SWC and the normalized difference vegetation index (NDVI) was very low because the atmosphere was close to saturation and the EF was relatively constant. In the dry season, the EF at both sites decreased with the SWC. The net ecosystem exchange (NEE) at Bange was largely depressed at noon, while this phenomenon did not occur at Lijiang. The saturated NEE at Bange was 24% of that at Lijiang. The temperature sensitivity coefficient of ecosystem respiration at Bange (1.7) was also much lower than that at Lijiang (3.4). The annual total NEE in 2015 was 21.8 and −230.0 g C m−2 yr−1 at Bange and Lijiang, respectively, and the NEE was tightly controlled by the NDVI at the two sites. The distinct differences in the water and CO2 fluxes at Bange and Lijiang are attributed to the large SWC difference and its effect on vegetation growth.

Based on the results from eleven flux sites during the third Tibetan Plateau (TP) Experiment (TIPEX III), land surface parameters and the turbulence characteristics of the atmospheric surface layer over the TP and surrounding region are analyzed. Monin-Obukhov similarity theory has been used to calculate the aerodynamic roughness length z0m and the excess resistance to heat transfer kB− 1 = ln(z0m/z0h), and the factors that cause variations of z0m and kB− 1 are investigated. The main sdrivers for the diurnal variations of surface albedo(α) at different sites are solar elevation, solar radiation, and soil moisture. The eddy correlation method is utilized to inversely calculate bulk transfer coefficients for momentum (CD) and heat (CH) at different sites. The relationships between CD and CH, and the wind speed at 10 m follow a power law for unstable stratification. For stable stratification, both CD and CH increase with increasing wind speed when wind speed is less than 5 m/s. Diurnal variations of turbulent fluxes are compared at different sites, and the relationships between turbulent fluxes and other variables are analyzed. Wind speed variance normalized by the friction velocity (σu/u*, σv/u*, σw/u*) for neutral stratification (Cu1,Cv1,Cw1), and temperature and humidity variance normalized by a temperature and humidity scale (σT/T*, σq/q*) under free convection (z/L

The cropland ecosystem in semiarid areas is sensitive to climate change. The accurate representation of crop phenology is important for predicting the carbon and water exchange process. The performance of a newly developed phenological model (SiBcrop) for simulations of carbon flux phenology in a semiarid area ecosystem was evaluated. The results showed that the SiBcrop improved the prediction for daily maximum gross primary production (GPP), and the days GPP reached the maximum value were closer to the observation, compared to SiB3. SiBcrop had a better prediction for both monthly total net ecosystem exchange (NEE) in the growing season than in the dormant season in semiarid areas. The day when the cumulative NEE predicted with SiBcrop became positive was closer to the observation. The observed start date of carbon uptake (CUstart) had a larger annual variation than did the end date of carbon uptake (CUend). SiBcrop had a better prediction for CUstart but poor for CUend, compared to SiB3. There was a longer carbon uptake period (CUP) predicted with SiBcrop than the observed results.

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.

Lake evaporation is an important link connecting the water cycle and the surface energy cycle and remains one of the most uncertain terms in the local catchment&rsquo, s water balance. Quantifying lake evaporation and its variability is crucial to improve water resource management and understand the response of the lake system towards climate change. In this study, we evaluated the performances of nine evaporation methods at different timescales and calibrated them by using the continuous eddy covariance (EC) observation data during 2015&ndash, 2018 over Erhai Lake, a highland open freshwater lake situated in the Dali valley, China. The nine evaporation methods could be classified into combination methods (Bowen-ratio energy budget, Penman, Priestley&ndash, Taylor, DeBruin&ndash, Keijman and Brutsaert&ndash, Stricker), solar radiation-based methods (Jensen&ndash, Haise and Makkink) and Dalton-based method (mass transfer and Ryan&ndash, Harleman) based on their parameterization schemes. The Dalton-based Ryan&ndash, Harleman method is most suitable for estimating evaporation at daily to weekly scales, while the combination methods and solar radiation-based method had good estimates at monthly timescale. After calibration, the biases of the Jensen&ndash, Haise and Ryan&ndash, Harleman method were slightly reduced, while the biases of the Makkink and mass transfer methods were reduced substantially. The calibrated Jensen&ndash, Haise method with small annual bias (&minus, 2.2~2.8%) and simple input variables was applied to estimate the long-term trend of evaporation during 1981&ndash, 2018. The annual total evaporation showed an insignificant increasing trend of 0.30 mm yr&minus, 1, mainly caused by the significant rising air temperature. This study showed the performance of evaporation methods over water bodies had large discrepancies on different time scales, which indicated the importance of the choice of evaporation methods and provided instruction for water resource management of this region under climate change.