Analysis on Precipitation Efficiency of the “21.7” Henan Extremely Heavy Rainfall Event

A record-breaking heavy rainfall event that occurred in Zhengzhou,Henan province during 19–21 July 2021 is simulated using the Weather Research and Forecasting Model,and the large-scale precipitation efficiency(LSPE)and cloud-microphysical precipitation efficiency(CMPE)of the rainfall are analyzed based on the model results.Then,the key physical factors that influenced LSPE and CMPE,and the possible mechanisms for the extreme rainfall over Zhengzhou are explored.Results show that water vapor flux convergence was the key factor that influenced LSPE.Water vapor was transported by the southeasterly winds between Typhoon In-Fa(2021)and the subtropical high,and the southerly flow of Typhoon Cempaka(2021),and converged in Zhengzhou due to the blocking by the Taihang and Funiu Mountains in western Henan province.Strong moisture convergence centers were formed on the windward slope of the mountains,which led to high LSPE in Zhengzhou.From the perspective of CMPE,the net consumption of water vapor by microphysical processes was the key factor that influenced CMPE.Quantitative budget analysis suggests that water vapor was mainly converted to cloud water and ice-phase particles and then transformed to raindrops through melting of graupel and accretion of cloud water by rainwater during the heavy precipitation stage.The dry intrusion in the middle and upper levels over Zhengzhou made the high potential vorticity descend from the upper troposphere and enhanced the convective instability.Moreover,the intrusion of cold and dry air resulted in the supersaturation and condensation of water vapor,which contributed to the heavy rainfall in Zhengzhou.

Integrated water vapor during active and break spells of monsoon and its relationship with temperature,precipitation and precipitation efficiency over a tropical site

Global Positioning System(GPS)measurements of integrated water vapor(IWV)for two years(2014 and 2015)are presented in this paper.Variation of IWV during active and break spells of Indian summer monsoon has been studied for a tropical station Hyderabad(17.4°N,78.46°E).The data is validated with ECMWF Re-Analysis(ERA)91 level data.Relationships of IWV with other atmospheric variables like surface temperature,rain,and precipitation efficiency have been established through cross-correlation studies.A positive correlation coefficient is observed between IWV and surface temperature over two years.But the coefficient becomes negative when only summer monsoon months(June,July,August,and September)are considered.Rainfall during these months cools down the surface and could be the reason for this change in the correlation coefficient.Correlation studies between IWV-precipitation,IWVprecipitation efficiency(P.E),and precipitation-P.E show that coefficients are-0.05,-0.10 and 0.983 with 95%confidence level respectively,which proves that the efficacy of rain does not depend only on the level of water vapor.A proper dynamic mechanism is necessary to convert water vapor into the rain.The diurnal variations of IWV during active and break spells have been analyzed.The amplitudes of diurnal oscillation and its harmonics of individual spell do not show clear trends but the mean amplitudes of the break spells are approximately double than those of the active spells.The amplitudes of diurnal,semidiurnal and ter-diurnal components during break spells are 1.08 kg/m^(2),0.52 kg/m;and 0.34 kg/m;respectively.The corresponding amplitudes during active spells are 0.68 kg/m^(2),0.41 kg/m;and 0.23 kg/m;.

Effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency

The effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency are investigated us ing grid-scale data from nine equilibrium sensitivity cloud-resolving model experiments driven without large-scale vertical velocity. The precipitation efficiencies are respectively defined in surface rainfall, cloud, and rain microphysical budgets. We mathematically and physically demonstrate the relationship between these precipitation efficiencies. The 2 ℃ increases in spatiotemporal invariant sea surface temperature （SST） from 27 ℃ to 29 ℃ and from 29 ℃ to 31 ℃, and the inclusion of diurnal SST difference 1 ℃ and the 1℃ increase in diurnal SST difference generate opposite changes in the precipitation efficiency by changing ice cloud-radiation interactions. The radiative and microphysical processes of ice clouds have opposite effects on the precipitation efficiency because of the rainfall increase associated with the reduction in the saturation mixing ratio caused by the exclusion of radiative effects and the decrease in rainfall related to the reduction in net condensation caused by the exclusion of deposition processes. The radiative effects of water clouds on the precipitation efficiency are statistically insensitive to the radiative effects of ice clouds.

Precipitation efficiency and its relationship to physical factors

The precipitation efficiency and its relationship to physical factors are examined by analyzing a two-dimensional cloud-resolving model simulation during TOGA COARE in this study. The basic physical factors include convective avail- able potential energy, water-vapor convergence, vertical wind shear, cloud ratio, sea surface temperature, air temperature, and precipitable water. Precipitation efficiencies do not show a close relationship to air temperature nor to sea surface tem- perature nor to precipitable water. The precipitation efficiency increases as the water-vapor convergence rate increases and vertical wind shear weakens, whereas it decreases as the convective available potential energy dissipates and anvil clouds develop.

Analysis on Summer Precipitation Efficiency in Shenyang

[Objective] The research aimed to analyze summer precipitation efficiency in Shenyang.[Method] By using the method which estimated the cloud water resource,based on the vertical accumulated liquid water content which was observed by 'QFW-1 dual-channel microwave radiometer' and the rain intensity data which had 1min interval and were inverted by 'particle laser-based optical measurement' (Parsivel),the precipitation efficiency in Shenyang area during July-August,2007 was analyzed.[Result] When the rain intensity I<7.5 mm/h,the precipitation efficiency E was stable and was during 3.2%-2.7%.The average value was 3.0%.When the rain intensity I ≥7.5 mm/h,the precipitation efficiency E presented the linear increasing as the rain intensity I increased.The bigger the rain intensity was,the more the remaining liquid water content in the air was,and the bigger the artificial precipitation potential was.[Conclusion] The research provided the guidance role for analyzing the cloud water resource in the air and the artificial precipitation potential.

Characteristics of Cloud Water Resource and Precipitation Efficiency of Hydrometeors over Northwest China

Understanding the characteristics of cloud water resource(CWR)and precipitation efficiency of hydrometeors(PEh)is imperative for the application of CWR in Northwest China.The atmospheric precipitable water(PW)in all four seasons and clouds and PEh in summer were studied with ERA-5 and CloudSat data in this region.The results show that topography,especially in the Tibetan Plateau,exerts significant impacts on the precipitation and PW in summer,since large amounts of clouds are distributed along the mountain ranges.The study region is divided into four typical areas:the monsoon area in eastern Northwest China(NWE),the Qilian Mountains area(QM),the Tianshan Mountains area(TM),and the Source of Three Rivers area(STR).Over the four areas,cloud top height(6.3 km)and cloud base height(3.3 km)over NWE are higher,and precipitating clouds are thicker(7 km)in the single-layer clouds.Liquid water content decreases with increasing altitude,while the ice water content first increases and then decreases.Liquid water path is higher over NWE(0.11 kg m^(−2))than over TM and STR(0.05 kg m^(−2)),and the ice water path is mainly concentrated within the range of 0.025–0.055 kg m^(−2).The PEh values are distributed unevenly and affected evidently by the terrain.Although the PEh values in the four typical areas(0.3–0.6)are higher than those in other regions,the CWR is relatively abundant and has a higher exploitation potential.Therefore,it is well-founded to exploit CWR for alleviating water shortages in these areas of Northwest China in summer.

Agronomic management practices in dryland wheat result in variations in precipitation use efficiency due to their differential impacts on the steps in the precipitation use process

Yield loss due to low precipitation use efficiency(PUE)occurs frequently in dryland crop production.PUE is determined by a complicated process of precipitation use in farmland,which includes several sequential steps:precipitation infiltrates into the soil,the infiltrated precipitation is stored in soil,the soil-stored precipitation is consumed through transpiration or evaporation,transpired precipitation is used to produce dry-matter,and finally dry-matter is re-allocated to grains.These steps can be quantified by six ratios:precipitation infiltration ratio(SW/SWe;SW,total available water;SWe,available soil water storage at the end of a specific period),precipitation storage ratio(SWe/P;P,effective precipitation),precipitation consumption ratio(ET/SW;ET,evapotranspiration),ratio of crop transpiration to evapotranspiration(T/ET;T,crop transpiration),transpiration efficiency(B/T;B,the increment of shoot biomass)and harvest index(Y/B;Y,grain yield).The final efficiency is then calculated as:PUE=SWe/P×SW/SWe×ET/SW×T/ET×B/T×Y/B.Quantifying each of those ratios is crucial for the planning and execution of PUE improvements and for optimizing the corresponding agronomic practices in a specific agricultural system.In this study,those ratios were quantified and evaluated under four integrated agronomic management systems.Our study revealed that PUE and wheat yield were significantly increased by 8–31%under manure(MIS)or biochar(BIS)integrated systems compared to either conventional farmers’(CF)or high N(HN)integrated systems.In the infiltration and storage steps,MIS and BIS resulted in lower SWe/P but higher SW/SWe compared with CF and HN.Regarding the consumption step,the annual ET/SW under MIS and BIS did not increase due to the higher ET after regreening and the lower ET before regreening compared with CF or HN.The T/ET was significantly higher under MIS and BIS than under CF or HN.In the last two steps,transpiration efficiency and harvest index were less strongly affected by the agronomic management system,although both values varied considerably across the different experimental years.Therefore,attempts to achieve higher PUE and yields in rainfed wheat through agronomic management should focus on increasing the T/ET and SW/SWe,while maintaining ET/SW throughout the year and keeping SWe/P relatively low at harvest time.

Water-use efficiency in response to simulated increasing precipitation in a temperate desert ecosystem of Xinjiang, China

Water-use efficiency（WUE） is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored the linkage between alteration in vegetation and WUE. Here, we analyzed the responses of leaf WUE, ecosystem carbon and water exchanges, ecosystem WUE, and plant community composition changes under normal conditions and also under extra 15% or 30% increases in annual precipitation in a temperate desert ecosystem of Xinjiang, China. We found that leaf WUE and ecosystem WUE showed inconsistent responses to increasing precipitation. Leaf WUE consistently decreased as precipitation increased. By contrast, the responses of the ecosystem WUE to increasing precipitation are different in different precipitation regimes： increasing by 33.9% in the wet year（i.e., the normal precipitation years）and decreasing by 4.1% in the dry year when the precipitation was about 30% less than that in the wet year.We systematically assessed the herbaceous community dynamics, community composition, and vegetation coverage to explain the responses of ecosystem WUE, and found that the between-year discrepancy in ecosystem WUE was consistent with the extent to which plant biomass was stimulated by the increase in precipitation. Although there was no change in the relative significance of ephemerals in the plant community, its greater overall plant biomass drove an increased ecosystem WUE under the conditions of increasing precipitation in 2011. However, the slight increase in plant biomass exerted no significant effect on ecosystem WUE in 2012. Our findings suggest that an alteration in the dominant species in this plant community can induce a shift in the carbon-and water-based economics of desert ecosystems.

Efects of Vertical Wind Shear, Radiation and Ice Microphysics on Precipitation Efciency during a Torrential Rainfall Event in China

The effects of vertical wind shear, radiation and ice microphysics on precipitation efficiency （PE） were investigated through analysis of modeling data of a torrential rainfall event over Jinan, China during July 2007. Vertical wind shear affected PE by changing the kinetic energy conversion between the mean and perturbation circulations. Clou^radiation interaction impacted upon PE, but the relationship related to cloud radiative effects on PE was not statistically significant. The reduction in deposition processes as- sociated with the removal of ice microphysics suppressed efficiency. The relationships related to effects of vertical wind shear, radiation and ice clouds on PEs defined in cloud and surface rainfall budgets were more statistically significant than that defined in the rain microphysical budget.

How precipitation and grazing influence the ecological functions of drought-prone grasslands on the northern slopes of the Tianshan Mountains, China?

Drought-prone grasslands provide a critical resource for the millions of people who are dependent on livestock for food security.However,this ecosystem is potentially vulnerable to climate change(e.g.,precipitation)and human activity(e.g.,grazing).Despite this,the influences of precipitation and grazing on ecological functions of drought-prone grasslands in the Tianshan Mountains remain relatively unexplored.Therefore,we conducted a systematic field investigation and a clipping experiment(simulating different intensities of grazing)in a drought-prone grassland on the northern slopes of the Tianshan Mountains in China to examine the influences of precipitation and grazing on aboveground biomass(AGB),soil volumetric water content(SVWC),and precipitation use efficiency(PUE)during the period of 2014–2017.We obtained the meteorological and SVWC data using an HL20 Bowen ratio system and a PR2 soil profile hydrometer,respectively.We found that AGB was clearly affected by both the amount and seasonal pattern of precipitation,and that PUE may be relatively low in years with either low or excessive precipitation.The PUE values were generally higher in the rapid growing season(April–July)than in the entire growing season(April–October).Overall,moderate grazing can promote plant growth under water stress conditions.The SVWC value was higher in the clipped plots than in the unclipped plots in the rapid growing season(April–July),but it was lower in the clipped plots than in the unclipped plots in the slow growing season(August–October).Our findings can enhance the understanding of the ecological effects of precipitation and grazing in drought-prone grasslands and provide data that will support the effective local grassland management.

Characterizing extreme drought and wetness in Guangdong,China using global navigation satellite system and precipitation data

As global temperature rises,the frequency of extreme climate events,e.g.,severe droughts and floods,has increased significantly and caused severe damage over the past years.To this regard,precipitation efficiency,a crucial meteorological parameter,could provide valuable insights for a better understanding of the patterns and characteristics of these extreme events.In this study,taking Guangdong province as an exemplary region,we first obtained long-term and high-resolution historical records of precipitation efficiency by integrating the observations from a dense network of Global Navigation Satellite System(GNSS)stations with precipitation data,and then characterized the extreme drought and wetness through climate indices.We found a distinct seasonal trend in precipitation efficiency in Guangdong,with annual fluctuations ranging from 10 to 25%.Notably,precipitation efficiency is higher in proximity to the Pearl River Delta Plain and gradually decreases towards the east and west.The occurrence of anomalous peaks and valleys in precipitation efficiency generally corresponds to dry and wet conditions,respectively.A total of 9 extreme wet events and 6 dry events occurred from January 2007 to May 2022,with durations from 3 to 6 months.Our results also demonstrated that both wet and dry frequencies exhibit an increasing trend with the expansion of the time scale,and the frequency of extreme events near the Pearl River Delta Plain surpasses that of other regions.Furthermore,the propagation time from meteorological anomalies to agricultural and hydrological anomalies is about 3 months.The periodic characteristics of meteorological anomalies are identified as the primary driver for other anomalous periodic patterns.Our work unveils the long-term dynamic behavior of precipitation efficiency,as well as the characteristics of extreme drought and wetness events in the regions characterized by intricate land–atmosphere interactions.

Crystallization behaviors of bayerite from sodium chromate alkali solutions

In order to clean production of chromium compounds, it is a critical process to remove aluminates and utilize aluminum compounds from artificial chromate alkali solutions. The effects of Na2 Cr O4 on the neutralization curve, Al（OH）3 precipitation efficiency and induction period of bayerite were investigated. The results indicate that the neutralization curve of the artificial chromate alkali solutions shows three distinct regions and its induction period is longer than that of pure sodium aluminate solutions at the same aluminum concentration. And the decreased temperature and volume fraction of CO2 enhance the particle size of bayerite β-Al（OH）3. Bayerite composed of agglomerates of rods and cone frustums was obtained from alkali metal chromate solutions with 28.5% CO2（volume fraction） at temperatures ranging from 50 °C to 70 °C. Coarse bayerite with particle size（d50） from 24.2 μm to 29.3 μm extremely has few impurities, which is suitable for comprehensive utilization.

Effects of film mulching regime on soil water status and grain yield of rain-fed winter wheat on the Loess Plateau of China

Shortages and fluctuations in precipitation are influential limiting factors for the sustainable cultivation of rain-fed winter wheat on the Loess Plateau of China. Plastic film mulching is one of the most effective water management practices to improve soil moisture, and may be useful in the Loess Plateau for increasing soil water storage. A field experiment was conducted from July 2010 to June 2012 on the Loess Plateau to investigate the effects of mulching time and rates on soil water storage, evapotranspiration （ET）, water use efficiency （WUE）, and grain yield. Six treatments were conducted： （1） early mulching （starting 30 days after harvest） with whole mulching （EW）; （2） early mulching with half mulching （EH）; （3） early mulching with no mulching （EN）; （4） late mulching （starting 60 days after harvest） with whole mulching （LW）; （5） late mulching with half mulching （LH）; and （6） late mulching with no mulching （LN）. EW increased precipitation storage efficiency during the fallow periods of each season by 18.4 and 17.8%, respectively. EW improved soil water storage from 60 days after harvest to the booting stage and also outperformed LN by 13.8 and 20.9% in each growing season. EW also improved spike number per ha by 13.8 and 20.9% and grain yield by 11.7 and 17.4% during both years compared to LN. However, EW decreased WUE compared with LN. The overall results of this study demonstrated that EW could be a productive and efficient practice to improve wheat yield on the Loess Plateau of China.

Spatial distribution of atmospheric water vapor and its relationship with precipitation in ,summer over the Tibetan Plateau

By using the observed monthly mean temperature and humidity dat, asets of 14 ra- diosonde stations and monthly mean precipitation data of 83 surface station., from 1979 to 2008 over the Tibetan Plateau （TP）, the relationship between the atmospheric water vapor （WV） and precipitation in summer and the precipitation conversion efficiency IPEC） over the TP are analyzed. The results are obtained as follows. （1） The summer WV decreases with increasing altitude, with the largest value area observed in the northeastern part of the TP, and the second largest value area in the southeastern part of the TP, while the northwestern part is the lowest value area. The summer precipitation decreases from southeast to north- west. （2） The summer WV presents two main patterns based on the EOF analysis： the whole region consistent-type and the north-south opposite-type. The north-south opposite-type of the summer WV is similar to the first EOF mode of the summer precipitation and both of their zero lines are located to the north of the Tanggula Mountains. （3） The summer precipitation is more （less） in the southern （northern） TP in the years with the distribution of deficient summer WV in the north while abundant in the south, and vice versa. （4） The PEC over the TP is between 3% and 38% and it has significant spatial difference in summer, which is obviously bigger in the southern TP than that in the northern TP.

Quantifying the Cloud Water Resource:Basic Concepts and Characteristics

The water in the air is composed of water vapor and hydrometeors,which are inseparable in the global atmosphere.Precipitation basically comes from hydrometeors instead of directly from water vapor,but hydrometeors are rarely focused on in previous studies.When assessing the maximum potential precipitation,it is necessary to quantify the total amount of hydrometeors present in the air within an area for a certain period of time.Those hydrometeors that have not participated in precipitation formation in the surface,suspending in the atmosphere to be exploited,are defined as the cloud water resource(CWR).Based on the water budget equations,we defined 16 terms(including 12 independent ones)respectively related to the hydrometeors,water vapor,and total water substance in the atmosphere,and 12 characteristic variables related to precipitation and CWR such as precipitation efficiency(PE)and renewal time(RT).Correspondingly,the CWR contributors are grouped into state terms,advection terms,and source/sink terms.Two methods are developed to quantify the CWR(details of which are presented in the companion paper)with satellite observations,atmospheric reanalysis data,precipitation products,and cloud resolving models.The CWR and related variables over North China in April and August 2017 are thus derived.The results show that CWR has the same order of magnitude as surface precipitation(Ps).The hydrometers converted from water vapor(Cvh)during the condensation process is the primary source of precipitation.It is highly correlated with Ps and contributes the most to the CWR over a large region.The state variables and advection terms of hydrometeors are two orders of magnitude lower than the corresponding terms of water vapor.The atmospheric hydrometeors can lead to higher PE than water vapor(several tens of percent versus a few percent),with a shorter RT(only a few hours versus several days).For daily CWR,the state terms are important,but for monthly and longer-time mean CWR,the source/sink terms(i.e.,cloud microphysical processes)contribute the largest;meanwhile,the advection terms contribute less for larger study areas.

Quantifying the Cloud Water Resource:Methods Based on Observational Diagnosis and Cloud Model Simulation

Based on the concepts of cloud water resource(CWR)and related variables proposed in the first part of this study,this paper provides details of two methods to quantify the CWR.One is diagnostic quantification(CWR-DQ)based on satellite observations,precipitation products,and atmospheric reanalysis data;and the other is numerical quantification(CWR-NQ)based on a cloud resolving model developed at the Chinese Academy of Meteorological Sciences(CAMS).The two methods are applied to quantify the CWR in April and August 2017 over North China,and the results are evaluated against all available observations.Main results are as follows.(1)For the CWR-DQ approach,reference cloud profiles are firstly derived based on the Cloud Sat/CALIPSO joint satellite observations for 2007–2010.The NCEP/NCAR reanalysis data in 2000–2017 are then employed to produce three-dimensional cloud fields.The budget/balance equations of atmospheric water substance are lastly used,together with precipitation observations,to retrieve CWR and related variables.It is found that the distribution and vertical structure of clouds obtained by the diagnostic method are consistent with observations.(2)For the CWR-NQ approach,it assumes that the cloud resolving model is able to describe the cloud microphysical processes completely and precisely,from which four-dimensional distributions of atmospheric water vapor,hydrometeors,and wind fields can be obtained.The data are then employed to quantify the CWR and related terms/quantities.After one-month continuous integration,the mass of atmospheric water substance becomes conserved,and the tempospatial distributions of water vapor,hydrometeors/cloud water,and precipitation are consistent with observations.(3)Diagnostic values of the difference in the transition between hydrometeors and water vapor(Cvh-Chv)and the surface evaporation(Es)are well consistent with their numerical values.(4)Correlation and bias analyses show that the diagnostic CWR contributors are well correlated with observations,and match their numerical counterparts as well,indicating that the CWR-NQ and CWR-DQ methods are reasonable.(5)Underestimation of water vapor converted from hydrometeors(Chv)is a shortcoming of the CWR-DQ method,which may be rectified by numerical quantification results or by use of advanced observations on higher spatiotemporal resolutions.