干旱胁迫对冬小麦水分关键期的生理特性和物质生产影响

以冬小麦品种“齐麦2号”为试材,在水分关键期(拔节期~扬花期),设计5个水分处理(T1处于适宜水平,T2、T3、T4、T5分别按照水分关键期常年降水量减少20%、50%、75%、100%进行一次性补水)和1个雨养对照水分控制试验,模拟研究不同程度干旱胁迫对水分关键期冬小麦光合生理特性、抗氧化酶活性及产量结构的影响。结果表明：轻度干旱胁迫会造成冬小麦叶片最大光合速率、气孔导度、胞间CO2浓度降低,气孔限制值升高,气孔因素是导致冬小麦叶片光合速率降低的主要原因;而当干旱胁迫达到重度时,胞间CO2浓度升高,气孔限制值降低,非气孔因素是导致冬小麦叶片光合速率降低的主要原因。轻度干旱胁迫会使得冬小麦叶片SOD酶、POD酶、CAT酶活性显著升高,从而减轻MDA含量升高对冬小麦叶片膜系统的损伤,复水后抗氧化酶活性和MDA含量均可恢复至正常水平,而重度干旱胁迫下冬小麦叶片SOD酶、POD酶、CAT酶活性不同程度降低,复水后抗氧化酶活性及MDA含量均无法恢复至正常水平,抗氧化酶系统遭受不可逆损伤。此外,水分关键期干旱胁迫还导致冬小麦灌浆速率降低、不孕穗率升高,理论产量大幅降低。研究结论可为科学评估干旱胁迫对冬小麦生长发育及产量形成的影响提供理论依据。     

水分胁迫/复水对谷子光合特性及产量影响

以谷子品种大金苗为研究对象,采用遮雨棚控水的大田试验方法,比较孕穗开花期和灌浆期水分胁迫/复水对叶片光合特性及产量影响,分析光合速率的限制因素,阐述光合速率、水分利用效率与产量的协同关系。结果表明:水分胁迫会导致谷子光合速率和产量下降,水分利用效率提高,随胁迫增强和持续时间延长,光合速率和产量下降幅度增大;水分胁迫后复水后,光合性能有所恢复,光合作用可产生补偿效应,水分胁迫越强和持续时间越长,补偿效应越低;轻度和持续时间短的水分胁迫,光合速率降低主要由气孔因素决定,随胁迫增强和持续时间延长,非气孔限制逐渐成为光合速率下降的主要原因;与孕穗开花期相比较,灌浆期水分胁迫对光合速率的影响更大且复水后光合性能恢复能力更低,光合速率与产量的协同关系更明显,产量对灌浆期水分胁迫更敏感。     

干旱胁迫对夏玉米叶片光合及叶绿素荧光的影响

选用华北地区大面积种植的夏玉米品种郑单958、承玉2号、鲁单981作为试验材料,通过研究干旱胁迫条件下的玉米叶片光合、叶绿素荧光等指标随着土壤水分的动态变化规律,以期为夏玉米干旱的生理生态变化监测及水分高效利用提供理论依据.研究发现,在土壤含水量70%左右时,随着土壤相对湿度的下降,上述3个夏玉米品种仍能保持其叶片水分状态.郑单958、承玉2号、鲁单981的叶片净光合速率在土壤水分中等条件下最大,分别为39.9、38.8、38.4 μmol CO2/m2 · s;在土壤相对湿度较低时,郑单958、承玉2号、鲁单981的叶片净光合速率下降趋势明显(P＜0.05).叶片水势变化规律为:在土壤相对湿度＞90%时,对水分胁迫郑单958、承玉2号不敏感,鲁单981敏感;在土壤相对湿度＜70%时,水分胁迫条件下承玉2号不敏感,而鲁单981、郑单958敏感.气孔导度(gs)变化规律:随着水分胁迫加剧,3个夏玉米品种气孔导度均下降,在土壤水分较高时,气孔导度变化规律不明显,在土壤水分较低时,气孔导度明显下降(P＜0.01),细胞间隙CO2浓度(Ci)随土壤水分胁迫加剧而上升.上述结果表明:与叶片的光合和水分状况相比,夏玉米的气孔对土壤水分的匮缺更为敏感.     

干旱胁迫对夏玉米叶片光合及叶绿素荧光的影响

选用华北地区大面积种植的夏玉米品种郑单958、承玉2号、鲁单981作为试验材料,通过研究干旱胁迫条件下的玉米叶片光合、叶绿素荧光等指标随着土壤水分的动态变化规律,以期为夏玉米干旱的生理生态变化监测及水分高效利用提供理论依据。研究发现,在土壤含水量70％左右时,随着土壤相对湿度的下降,上述3个夏玉米品种仍能保持其叶片水分状态。郑单958、承玉2号、鲁单981的叶片净光合速率在土壤水分中等条件下最大,分别为39．9、38．8、38．4μmolCO2／m^2·s;在土壤相对湿度较低时,郑单958、承玉2号、鲁单981的叶片净光合速率下降趋势明显（P〈0．05）。叶片水势变化规律为：在土壤相对湿度〉90％时,对水分胁迫郑单958、承玉2号不敏感,鲁单981敏感;在土壤相对湿度〈70％时,水分胁迫条件下承玉2号不敏感,而鲁单981、郑单958敏感。气孔导度（g1）变化规律：随着水分胁迫加剧,3个夏玉米品种气孔导度均下降,在土壤水分较高时,气孔导度变化规律不明显,在土壤水分较低时,气孔导度明显下降（P〈0．01）,细胞间隙CO2浓度（Ci）随土壤水分胁迫加剧而上升。上述结果表明：与叶片的光合和水分状况相比,夏玉米的气孔对土壤水分的匮缺更为敏感。     

土壤水分胁迫对冬小麦旗叶光合特性的影响

以土壤水分适宜做对照(CK),轻度水分胁迫(50%～70%)、中度水分胁迫(小于50%)3种处理在河北固城可控式土壤水分试验场,选择冬小麦灌浆初期的晴朗天气,采用Li-Cor 6400便携式光合作用仪,观测了3种处理的冬小麦旗叶光合作用参数的日变化。试验结果表明:土壤水分适宜时冬小麦旗叶净光合速率的日变化为"单峰型",未出现明显的"午休"现象,水分胁迫的处理都呈"双峰型",中度胁迫反而比轻度胁迫光合"午休"要短2h;3种处理的蒸腾速率日变化都呈"双峰型",气孔导度是反映叶片气体交换的重要指标,蒸腾速率与气孔导度成极显著正相关;土壤水分适宜或土壤干旱时冬小麦旗叶对环境变化的应变性较迟钝;轻度水分胁迫时冬小麦旗叶净光合速率比CK高2.8%～9.0%,蒸腾速率与CK基本相近,水分利用效率(WUE)比CK高10.6%～12.9%,这可能是一定程度的水分胁迫下冬小麦节水增产的生理调节机理。     

半干旱区黑膜覆盖对马铃薯光合特性及产量的影响

为探讨黑膜覆盖对马铃薯光合过程和产量的影响,以品种"新大坪"为试材进行试验,对比分析黑膜覆盖(PM)处理与裸地对照(CK)下马铃薯净光合速率(P_n)、气孔导度(G_s)、胞间CO_2浓度(Ci)、蒸腾速率(Tr)、水分利用效率(WUE)及产量等变化特征。结果表明:PM处理下叶片净光合速率和气孔导度在分枝期、花序形成期及开花期均较CK增大,但不同生育期增幅差异显著,其中净光合速率在分枝期增幅最大,为63%,而气孔导度最大增幅出现在花序形成期,为38%,开花期二者增幅均最小。胞间CO_2浓度PM处理在分枝期较CK降低12%,而花序形成期、开花期较CK分别提高1%、6%。蒸腾速率PM处理在分枝期、开花期较CK分别提高44%、19%,而花序形成期则下降4%。3个生育期叶片水分利用效率PM处理均高于CK,其中花序形成期提升显著。与CK相比,PM处理下的叶片光补偿点(LCP)、光饱和点(LSP)及最大净光合速率(Pmax)均有所降低,而表观量子效率(AQE)、暗呼吸速率(Rd)和产量均有所升高,其中马铃薯产量提升近3倍,增产效果明显。说明在黄土高原半干旱区,通过采用黑膜覆盖来影响马铃薯光合过程,能够显著提高马铃薯产量。     

水分胁迫对扬花期冬小麦光合特性和干物质生产及产量的影响

试验于2016-2017年冬小麦生长季在临沂设施农业气象试验站自动控制遮雨棚内的水分控制场进行,以"齐麦2号"为试材,在水分关键期设计5个梯度水分处理(T1适宜水平,T2、T3、T4、T5分别按照冬小麦水分关键期比常年降水量减少20%、50%、75%、100%一次性补水)和1个雨养对照的水分控制试验,模拟研究不同程度干旱胁迫对扬花期冬小麦光合特性、干物质生产及产量的影响。结果表明:干旱胁迫下,扬花期冬小麦叶片叶绿素a含量、光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r),株高、叶面积、地上部分总干重均呈降低趋势,且干旱胁迫越重,降低幅度越大,T5处理叶绿素a含量、P_n、G_s、T_r、株高、叶面积及地上部分总干重分别较T1处理降低33.6%、67.4%、90.9%、84.6%、43.9%、19.1%和33.3%;随着干旱胁迫的加剧,水分利用效率(WUE)则呈先增加后降低的趋势,并在轻度干旱胁迫时达到最高;干旱胁迫促进植株养分向叶、鞘转移,减少对茎、穗的养分供给,不利于冬小麦产量提高,此外,扬花期干旱胁迫还造成冬小麦灌浆速率降低、不孕穗率升高,理论产量大幅降低。     

水分关键期干旱胁迫对冬小麦矿质元素积累、产量和品质的影响

干旱是制约我国粮食产量和品质提升的主要农业气象灾害之一。土壤水分与矿质元素交互作用，共同影响冬小麦的生长发育及产量、品质，探究水分关键期冬小麦叶片矿质元素积累、产量和籽粒品质对不同程度干旱胁迫的响应，对科学施肥和干旱灾害防御具有现实意义。本文以冬小麦品种“齐麦2号”为试材，在水分关键期(拔节—扬花期)设计5个梯度的水分控制试验(T1处理为适宜水平，T2、T3、T4处理分别按照基准补水量75.0 mm的80%、50%、25%一次性补水，T5处理不补水)，模拟研究水分关键期干旱胁迫对冬小麦叶片氮、磷、钾矿质元素积累和光合色素、光合参数以及产量和籽粒品质的影响。结果表明：水分控制期间至复水后，T1处理下冬小麦叶片全氮、全磷、光合色素含量及最大净光合速率(Maximum Net Photosynthetic Rate,P_nmax)、表观量子效率(Apparent Quantum Efficiency,AQE)、光饱和点(Light Saturation Point,LSP)均最高，受干旱胁迫影响，T2、T3、T4和T5处理下上述要素均显著降低，且干旱胁迫程度越重降低幅度越...     

不同土壤水分对向日葵光合光响应的影响

以食用向日葵为试验材料,大田试验采取人为控制土壤水分在胁迫、适宜和过湿 (土壤田间持水量的40%~54.9%,55%~69.9%和70%~90%) 条件下,研究了向日葵3个生育期 (二对真叶—花序形成期、花序形成—开花期、开花—成熟期) 的光合光响应特性。结果表明:在试验设置光强条件下,各生育期净光合速率随着光合有效辐射的增加而增加,同等的光合有效辐射下净光合速率也随着土壤水分的减少依次降低,尤其是随着光合有效辐射的增大愈加明显。土壤湿度对最大净光合速率和表观量子效率的影响并不是同步的,最大净光合速率随着土壤湿度的增加而增大,而表观量子效率在一定程度的水分胁迫情况下出现最大值。不同的土壤水分含量对光补偿点和光饱和点影响不同,光饱和点随着土壤水分的增加而增加,光补偿点却相反,表明水分胁迫使向日葵可利用光的范围缩小,而适宜水分则扩大了光的利用范围,更有利于干物质积累。暗呼吸速率随着植物的生长进程逐渐降低,不同生育期的水分胁迫均导致暗呼吸速率降低。     

多情景土壤水分胁迫对固城夏玉米产量的定量影响评估

基于河北省固城生态与农业气象试验站2013—2015年夏玉米田间水分控制试验资料,分多情景模拟自然环境,研究了水分充足条件下夏玉米穗粒重随发育进程(DVS)的变化特征,对比分析了不同持续时间、不同发育阶段、不同程度水分胁迫对产量的影响,并建立了不同情景水分胁迫下土壤相对湿度与产量的定量关系模型。结果表明,在水分充足条件下,夏玉米穗粒重随DVS的增加呈现"慢—快—慢"的增长特征,其中乳熟—乳熟后10d的增长幅度和增长速率均为最大;水分胁迫发生在抽雄后10d—乳熟阶段,粒重减少最明显。夏玉米产量与出苗—拔节(阶段Ⅰ)、拔节—抽雄(阶段Ⅱ)、抽雄—成熟(阶段Ⅲ)以及[阶段Ⅰ+阶段Ⅱ]和[阶段Ⅱ+阶段Ⅲ]5个不同时段土壤相对湿度均呈线性显著正相关关系,其关系模型表明,水分胁迫程度越严重、持续时间越长,产量减少幅度越大,不同阶段、相同胁迫程度和持续时间对产量的影响总体表现为:阶段Ⅰ阶段Ⅱ阶段Ⅲ[阶段Ⅰ+阶段Ⅱ][阶段Ⅱ+阶段Ⅲ],以上阶段土壤相对湿度下降10%,产量分别减少89.7g/m2、122.7g/m2、129.8g/m2、133.7g/m2和144.4g/m2,减幅为22.8%～36.8%。     

UV-B辐射增强对不同品种花生结荚期生理特性日变化的影响

以3个花生品种（开农49号、64号和69号）为材料,通过大田模拟试验,研究UV-B辐射增强对花生结荚期叶片的净光合速率（P_n）、气孔导度（G_s）、胞间CO₂浓度（C_i）、蒸腾速率（T_r）和水分利用效率（E_wu）日变化的影响,为筛选高产、抗旱、抗UV-B辐射花生品种提供依据.UV-B辐射设2个水平即自然光（CK,1.5 kJ·m^-2）和UV-B增强20%（T,1.8 kJ·m^-2）.结果表明,UV-B辐射增强明显抑制花生的光合作用和蒸腾作用,与对照相比,UV-B增强条件下,开农49号、64号和69号P_n日均值分别降低19.4%、27.8%、24.7%;G_s日均值降低26.7%、42.9%、28.6%;C_i日均值降低27.2%、20.4%、23.1%;T_r日均值降低17.8%、23.3%、25.1%;E_wu日均值降低16.6%、23.2%、23.9%.UV-B辐射增强对3个品种生长都具有抑制效应,但品种间存在一定的敏感性差异,其中开农49号最不敏感,因此,开农49号在抗UV-B辐射方面比其他2个品种具有更大的优势.     

Comprehensive modeling of monthly mean soil temperature using multivariate adaptive regression splines and support vector machine

Soil temperature (T _s) and its thermal regime are the most important factors in plant growth, biological activities, and water movement in soil. Due to scarcity of the T _s data, estimation of soil temperature is an important issue in different fields of sciences. The main objective of the present study is to investigate the accuracy of multivariate adaptive regression splines (MARS) and support vector machine (SVM) methods for estimating the T _s. For this aim, the monthly mean data of the T _s (at depths of 5, 10, 50, and 100 cm) and meteorological parameters of 30 synoptic stations in Iran were utilized. To develop the MARS and SVM models, various combinations of minimum, maximum, and mean air temperatures (T _min, T _max, T); actual and maximum possible sunshine duration; sunshine duration ratio (n, N, n/N); actual, net, and extraterrestrial solar radiation data (R _s, R _n, R _a); precipitation (P); relative humidity (RH); wind speed at 2 m height (u ₂); and water vapor pressure (V_p) were used as input variables. Three error statistics including root-mean-square-error (RMSE), mean absolute error (MAE), and determination coefficient (R ²) were used to check the performance of MARS and SVM models. The results indicated that the MARS was superior to the SVM at different depths. In the test and validation phases, the most accurate estimations for the MARS were obtained at the depth of 10 cm for T _max, T _min, T inputs (RMSE = 0.71 °C, MAE = 0.54 °C, and R ² = 0.995) and for RH, V _p, P, and u ₂ inputs (RMSE = 0.80 °C, MAE = 0.61 °C, and R ² = 0.996), respectively.     

Periodic solutions of the set of equations governing the nonadiabatic convection of dry isolated thermals

The changes with timet of a temperature deviation δT(t,α) and of a vertical velocityW _i(t,α) of an isolated dry thermal have been investigated theoretically. Solutions for the functionW _i(t, α) have been derived for stable and unstable environmental stratifications. Comparing these solutions with the corresponding ones for the rise of an adiabatic thermal yield some interesting conclusions. Firstly, there is the evident relation between the rate of entrainment of environmental air (expressed by the parameter α=(1/M _i) dM _i/dz whereM _i is the mass of the thermal) and the vertical velocity of the thermal: an increase in α decreases the velocity. Two similar thermals in stably stratified surroundings, one of them moving adiabatically (α=0) the other nonadiabatically (α>0), would rise for the same length of timet ₂=π/N, whereN is a typical Brunt-Väisälä frequency, but with different velocities and to different heights: the ascent timet ₂ depends only on environmental parameters. In an unstable stratification, the vertical non-adiabatic velocity of the thermal, instead of increasing without limit, tends towards a finite asymptotic velocity $$W_t (\infty ) = (\sqrt { - \mathcal{N}^2 } )/\alpha $$ the value of which depends upon both the stratification of the surroundings and upon the entrainment rate α. In a real atmosphere, where additional retarding forces exist, the motion will certainly be damped.     

Carbon and water flux responses to physiology by environment interactions: a sensitivity analysis of variation in climate on photosynthetic and stomatal parameters

Sensitivity of carbon uptake and water use estimates to changes in physiology was determined with a coupled photosynthesis and stomatal conductance (g _s) model, linked to canopy microclimate with a spatially explicit scheme (MAESTRA). The sensitivity analyses were conducted over the range of intraspecific physiology parameter variation observed for Acer rubrum L. and temperate hardwood C₃ (C₃) vegetation across the following climate conditions: carbon dioxide concentration 200–700 ppm, photosynthetically active radiation 50–2,000 μmol m^?2 s^?1, air temperature 5–40 °C, relative humidity 5–95 %, and wind speed at the top of the canopy 1–10 m s^?1. Five key physiological inputs [quantum yield of electron transport (α), minimum stomatal conductance (g ₀), stomatal sensitivity to the marginal water cost of carbon gain (g ₁), maximum rate of electron transport (J _max), and maximum carboxylation rate of Rubisco (V _cmax)] changed carbon and water flux estimates ≥15 % in response to climate gradients; variation in α, J _max, and V _cmax input resulted in up to ~50 and 82 % intraspecific and C₃ photosynthesis estimate output differences respectively. Transpiration estimates were affected up to ~46 and 147 % by differences in intraspecific and C₃ g ₁ and g ₀ values—two parameters previously overlooked in modeling land–atmosphere carbon and water exchange. We show that a variable environment, within a canopy or along a climate gradient, changes the spatial parameter effects of g ₀, g ₁, α, J _max, and V _cmax in photosynthesis-g _s models. Since variation in physiology parameter input effects are dependent on climate, this approach can be used to assess the geographical importance of key physiology model inputs when estimating large scale carbon and water exchange.     

Potential future changes in water limitations of the terrestrial biosphere

This study explores the effects of atmospheric CO₂ enrichment and climate change on soil moisture (W _r ) and biome-level water limitation (L _TA), using a dynamic global vegetation and water balance model forced by five different scenarios of change in temperature, precipitation, radiation, and atmospheric CO₂ concentration, all based on the same IS92a emission scenario. L _TA is defined as an index that quantifies the degree to which transpiration and photosynthesis are co-limited by soil water shortage (high values indicate low water limitation). Soil moisture decreases in many regions by 2071–2100 compared to 1961–1990, though the regional pattern of change differs substantially among the scenarios due primarily to differences in GCM-specific precipitation changes. In terms of L _TA, ecosystems in northern temperate latitudes are at greatest risk of increasing water limitation, while in most other latitudes L _TA tends to increase (but again varies the regional pattern of change among the scenarios). The frequently opposite direction of change in W _r and L _TA suggests that decreases in W _r are not necessarily felt by actual vegetation, which is attributable mainly to the physiological vegetation response to elevated CO₂. Without this beneficial effect, the sign of change in L _TA would be reversed from predominantly positive to predominantly negative.     

étude expérimentale de la couche limite au-dessus d'un relief modéré proche d'une chaîne de montagne

Doppler sodar derived values of the temperature structure parameter C _infT ^sup2 , the vertical velocity variance ¯′w ², and the rate of dissipation of turbulent energy ?, were measured during unstable conditions above the Lannemezan heterogeneous site. The vertical profiles of these turbulent parameters, normalized by the classical convective scales are compared with those obtained using the same acoustic sounder above an homogeneous site during convective conditions. The typical decrease of C _infT ^sup2 as Z ^-4/3 is partially verified on the heterogeneous site: for the lower levels, C _infT ^sup2 exhibits an increase with Z whereas for the intermediate levels C _infT ^sup2 . decreases as Z ^-4/3. For the upper levels, C _infT ^sup2 increases with Z due to a signal-to-noise ratio lower than 1. The vertical profiles of ¯′w ² above the two sites are rather similar. However, near the base of the convective inversion Z _i , the values measured on the heterogeneous site are more scattered. The same scattering is also observed with the ? values; moreover, for the lower levels (Z<0.17Z _i ) the increase of ? as Z decreases is more important at the homogeneous site than at the heterogeneous one. It is suggested that these particular features observed at lower levels above the heterogeneous site are mainly related to a complex local boundary layer induced by the near environment of the sodar (vegetation and relief).     

卫星遥感结合气象资料计算的青藏高原地面感热特征分析

本文选取1981年7月至2012年12月美国国家航空和航天局（NASA）制作的归一化的动态植被指数（NDVI）资料、根据NDVI值计算地表热力输送系数（C_H）的参数化关系式（C_H-I_NDV）和青藏高原70个常规气象观测资料,计算了青藏高原全区的逐月地表热力输送系数（C_H）,讨论了其时空分布特征,并在此基础上计算了高原70个常规台站的感热通量（SSHF）序列,并与已有感热资料进行了对比。随后,探讨了地面感热通量的气候特征及其年际变化与气候因子的关系。结果表明:高原地区的C_H值具有明显的空间差异和季节差异,表现为东高西低、夏季大、冬季小的特点。感热的年际变化在冬季主要响应于地气温差的变化,夏季则受地面风速影响较大;由于风速减小趋缓,地气温差增大,变化趋势在2003年前后由减弱趋势转变为增强趋势,这种趋势的转变最早发生在2001年秋季,且在高原全区具有较好的一致性。     

Stability Effects on Heat and Moisture Fluxes at Sea

During the 1996 ASGAMAGE experiment we measured windspeed, air temperature T_a, watertemperature T_s, humidity and the momentum,heat and moisture fluxes at a research platform offthe Dutch coast. For each quantity we used several(sets of) instruments simultaneously. This allowed usto make an extensive assessment of the quality of themeasurements and to find optimal values for thevarious quantities for each run. From these values wecalculated C_H and C_E, theStanton and Dalton numbers, and reduced them to 10-mheight and neutral conditions. For this reductionwe made a separate analysis for the effect ofinclusion or non-inclusion of the assumption that theroughness length for heat or moisture is the same forthe neutral and non-neutral cases. Differences inthe reduced data due to this assumption turned out tobe well within the measurement error.For C_H we distinguished three separategroups of data: stable (A), unstable with_{a s} (B) and unstablewith thetas;_a > _s (C), with indicating the potential temperature.The stable data separate into two groups, depending onwater temperature and/or the wave field. The data ofgroup B showed a relation with wave age. The data ofgroup C consistently gave negative values forC_H, a result that might indicate conversion oflatent heat into sensible heat through condensation ofwater vapour just above the water surface. An attemptto re-analyse the data in terms of density fluxes,combining the effects of heat and moisture, still gavenegative transfer coefficients for group C.For the moisture flux we found the more conventionalresult of a separation in stable and unstable values;these categories showed a clear difference, but notrends with, for example, wind speed.We conclude that standard Monin-Obukhov similaritytheory cannot explain our data.     

“碧利斯”（2006）暴雨过程降水强度和降水效率分析

利用2006年第4号强热带风暴“碧利斯”登陆过程的高分辨率数值模拟资料,结合三维地面降水诊断方程和降水效率公式,研究了“碧利斯”登陆后引发的局地暴雨过程,重点分析了此次局地暴雨过程的降水强度和降水效率及其与宏微观物理因子的联系。结果表明,降水强度越强,降水效率越高,但两者并非一一对应的线性关系,随着降水强度增大,降水效率增高的趋势逐渐变缓;伴随暴雨系统快速发展,降水强度和降水效率均显著增强,而主要降水源/汇项的时间变化要复杂得多;暴雨发生前时段与发生时段降水物理过程存在显著差异,发生前,较明显的水汽辐合显著加湿局地大气,并通过微物理转化支持降水云系发展,液相水凝物辐合对降水云系快速发展贡献明显,固相水凝物辐合贡献不显著,较强的“云滴与雨滴碰并（P_racw）”微物理过程同液相水凝物明显辐合可能有直接关系,“霰融化造成雨滴增长（P_gmlt）”仅为P_racw的27%,发生时段,进一步明显加强的水汽辐合依旧是主要降水来源,而汇项发生了明显变化,同时,微物理转化过程与发生前比更活跃,尤其是P_racw和P_gmlt,其中,P_gmlt增强更明显,其值接近P_racw的50%。     

Spatial dependence of diurnal temperature range trends on precipitation from 1950 to 2004

This paper analyzes the spatial dependence of annual diurnal temperature range (DTR) trends from 1950–2004 on the annual climatology of three variables: precipitation, cloud cover, and leaf area index (LAI), by classifying the global land into various climatic regions based on the climatological annual precipitation. The regional average trends for annual minimum temperature (T _min) and DTR exhibit significant spatial correlations with the climatological values of these three variables, while such correlation for annual maximum temperature (T _max) is very weak. In general, the magnitude of the downward trend of DTR and the warming trend of T _min decreases with increasing precipitation amount, cloud cover, and LAI, i.e., with stronger DTR decreasing trends over drier regions. Such spatial dependence of T _min and DTR trends on the climatological precipitation possibly reflects large-scale effects of increased global greenhouse gases and aerosols (and associated changes in cloudiness, soil moisture, and water vapor) during the later half of the twentieth century.