Dimension Characteristics and Precipitation Efficiency of Cumulonimbus Clouds in the Region Far South from the Mei-Yu Front over the Eastern Asian Continent

Abstract Dimension characteristics in precipitation properties of cumulonimbus clouds are basic parameters in understanding the vertical transport of water vapor in the atmosphere. In this study, the dimension characteristics and precipitation efficiency of cumulonimbus clouds observed in the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) Huaihe River Basin Experiment (HUBEX) are studied using data from X-band Doppler radars and upper-air soundings. The maximum echo area (EAmax) of the cumulonimbus clouds ranged from 0.5 to 470 km2, and the maximum echo top (ETmax) ranged from 2 to 19 km. The total number of cells (TNC) within the cumulonimbus clouds over their lifetime was from 1 to 25. The ETmax, TNC, area time integral (ATI), and total rainfall amount (Rtot) strongly correlate with the EAmax of the cumulonimbus clouds. The cell-averaged ATI (ATIcell = ATI/TNC), maximum rainfall intensity (RImax), and cell-averaged rainfall amount (Rcell = Rtot/TNC) increase when the EAmax is smaller than 100 km2. On the other hand, they are almost constant when the EAmax is larger than 100 km2. The rain productivity of small clouds (<100 km2 in EAmax) increases not only by the increase of the TNC but also by the intensification of cells, while that of large cumulonimbus clouds (>100 km2 in EAmax) increases by the increase of the TNC rather than by the intensification of cells. In the present study, precipitation efficiency (ɛp) is defined as the ratio of the total rainfall amount (Rtot) to the total water vapor amount ingested into the cloud through the cloud base (Vtot). The ɛp was calculated for six clouds whose vertical velocity data at the cloud-base level were deduced by dual-Doppler analysis throughout their lifetime. The ɛp ranged from 0.03% to 9.31% and exhibited a strong positive correlation with the EAmax. This indicates that more than 90% of the water vapor that enters the clouds through the cloud base is consumed to moisten the atmosphere and less than 10% is converted to precipitation and returned to the ground. The cumulonimbus clouds in the region far south from the mei-yu front over the eastern Asian continent efficiently transport water vertically and humidify the upper troposphere.

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Characteristics of Stable Hydrogen and Oxygen Isotopes in Precipitation over the Jiaolai Plain, and its Water Vapor Sources

10.22541/au.160681001.15900411/v1 ◽

2020 ◽

Author(s):

Ying Wang ◽

Buli Cui ◽

Dongsheng Li ◽

Yaxuan Wang

Keyword(s):

Water Vapor ◽

Oxygen Isotopes ◽

Water Cycle ◽

Sampling Period ◽

Global Network ◽

Cloud Base ◽

Mountainous Area ◽

Vapor Source ◽

Hydrogen And Oxygen Isotopes ◽

Regional Water

Precipitation is the sole input of regional water resources in mountainous or hilly areas that are not traversed by large rivers. A prerequisite for using isotopic techniques to study the regional water cycle of a mountainous area is to examine the stable isotopic composition of its precipitation. The findings are of great significance for in-depth understanding of the water-cycle processes. In this study, each event of precipitation was sampled and used to investigate the characteristics of stable hydrogen and oxygen isotopes (δ2H and δ18O, respectively) in precipitation on the Jiaolai Plain and its surrounding areas. NCEP/NCAR data was used for the wind speed and direction, relative humidity, and precipitable amount in the study area during the sampling period. The water vapor sources of precipitation over the plain were revealed through a comparative analysis of seasonal variations in precipitation isotopes, between the Global Network of Isotopes in Precipitation (GNIP) stations located along different vapor transport paths. The results showed that the local meteoric water line (LMWL) was δ2H = 6.38 δ18O + 0.72, with a gradient less than 8. This indicated that the precipitation process was affected by non-equilibrium evaporation occurred when the drops fell below the cloud base. Significant temperature and amount effects existed in the δ18O of precipitation, although the altitude effect was not significant. The water vapor source of the precipitation was controlled predominantly by the East Asian Monsoon from June to September, with the main source being evaporation from the adjacent Pacific Ocean. The plain was controlled by Westerlies from October through May, with the predominant vapor source being local evaporation. Water vapor from the polar region had minimal impact. During the sampling period, water vapor brought by Typhoon Lekima produced heavy precipitation on the plain. There was a significant depletion of δ18O in the precipitation at that time, indicating the existence of the cloud–rain zonal effect. These findings can serve as the basis for studying surface water–groundwater–seawater transformation.

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Estimating Water Vapor Using Signals from Microwave Links below 25 GHz

Remote Sensing ◽

10.3390/rs13081409 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1409

Author(s):

Kun Song ◽

Xichuan Liu ◽

Taichang Gao ◽

Peng Zhang

Keyword(s):

Water Vapor ◽

Weather Forecasting ◽

Water Cycle ◽

Correlation Coefficients ◽

Support Vector ◽

Vapor Density ◽

Measurement Resolution ◽

Sensing Model ◽

Numerical Weather Forecasting ◽

Mean Square Errors

Water vapor is a key element in both the greenhouse effect and the water cycle. However, water vapor has not been well studied due to the limitations of conventional monitoring instruments. Recently, estimating rain rate by the rain-induced attenuation of commercial microwave links (MLs) has been proven to be a feasible method. Similar to rainfall, water vapor also attenuates the energy of MLs. Thus, MLs also have the potential of estimating water vapor. This study proposes a method to estimate water vapor density by using the received signal level (RSL) of MLs at 15, 18, and 23 GHz, which is the first attempt to estimate water vapor by MLs below 20 GHz. This method trains a sensing model with prior RSL data and water vapor density by the support vector machine, and the model can directly estimate the water vapor density from the RSLs without preprocessing. The results show that the measurement resolution of the proposed method is less than 1 g/m3. The correlation coefficients between automatic weather stations and MLs range from 0.72 to 0.81, and the root mean square errors range from 1.57 to 2.31 g/m3. With the large availability of signal measurements from communications operators, this method has the potential of providing refined data on water vapor density, which can contribute to research on the atmospheric boundary layer and numerical weather forecasting.

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Why sometimes its simply sunny (in the trades)

10.5194/egusphere-egu21-15408 ◽

2021 ◽

Author(s):

Bjorn Stevens ◽

Ilya Serikov ◽

Anna Lea Albright ◽

Sandrine Bony ◽

Geet George ◽

...

Keyword(s):

Boundary Layer ◽

Water Vapor ◽

Marine Boundary Layer ◽

Cloud Base ◽

Lidar Signal ◽

Cloud Base Height

<p>Cloud free skies are rare in the trades. &#160;We analyze conditions in which cloud-free conditions prevail. &#160;For this purpose Raman water vapor measurements from the Barbados Cloud Observatory, complemented by ship-based measurements during EUREC4A are used to explore water vapor variability in the marine boundary layer. &#160; We explore the consistency of the inferred cloud base height with estimates of temperature and water vapor from the lidar signal, and examine the co-variability of these quantities. &#160;After having established the properties of these measurements, we seek to use them as well as others, to explain in what ways periods of cloud-free conditions are maintained, investigating the hypothesis that only when the wind stills is it simply sunny.</p>

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On the Relationship between Intensity and Rainfall Distribution in Tropical Cyclones Making Landfall over China

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-16-0334.1 ◽

2017 ◽

Vol 56 (10) ◽

pp. 2883-2901 ◽

Cited By ~ 26

Author(s):

Zifeng Yu ◽

Yuqing Wang ◽

Haiming Xu ◽

Noel Davidson ◽

Yandie Chen ◽

...

Keyword(s):

Tropical Cyclones ◽

Rain Rate ◽

Vertical Wind Shear ◽

Intensity Change ◽

Total Rainfall ◽

Rainfall Distribution ◽

Rain Area ◽

Maximum Rainfall ◽

Rain Rates ◽

The Relationship

AbstractTRMM satellite 3B42 rainfall estimates for 133 landfalling tropical cyclones (TCs) over China during 2001–15 are used to examine the relationship between TC intensity and rainfall distribution. The rain rate of each TC is decomposed into axisymmetric and asymmetric components. The results reveal that, on average, axisymmetric rainfall is closely related to TC intensity. Stronger TCs have higher averaged peak axisymmetric rain rates, more averaged total rain, larger averaged rain areas, higher averaged rain rates, higher averaged amplitudes of the axisymmetric rainfall, and lower amplitudes of wavenumbers 1–4 relative to the total rainfall. Among different TC intensity change categories, rapidly decaying TCs show the most rapid decrease in both the total rainfall and the axisymmetric rainfall relative to the total rain. However, the maximum total rain, maximum rain area, and maximum rain rate are not absolutely dependent on TC intensity, suggesting that stronger TCs do not have systematically higher maximum rain rates than weaker storms. Results also show that the translational speed of TCs has little effect on the asymmetric rainfall distribution in landfalling TCs. The maximum rainfall of both the weaker and stronger TCs is generally located downshear to downshear left. However, when environmental vertical wind shear (VWS) is less than 5 m s−1, the asymmetric rainfall maxima are more frequently located upshear and onshore, suggesting that in weak VWS environments the coastline could have a significant effect on the rainfall asymmetry in landfalling TCs.

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Subcloud and Cloud-Base Latent Heat Fluxes during Shallow Cumulus Convection

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0122.1 ◽

2019 ◽

Vol 77 (3) ◽

pp. 1081-1100 ◽

Cited By ~ 1

Author(s):

Neil P. Lareau

Keyword(s):

Boundary Layer ◽

Water Vapor ◽

Latent Heat ◽

Surface Fluxes ◽

Heat Fluxes ◽

Cloud Base ◽

Cumulus Convection ◽

Mixing Ratio ◽

Convective Boundary ◽

Water Vapor Mixing Ratio

Abstract Doppler and Raman lidar observations of vertical velocity and water vapor mixing ratio are used to probe the physics and statistics of subcloud and cloud-base latent heat fluxes during cumulus convection at the ARM Southern Great Plains (SGP) site in Oklahoma, United States. The statistical results show that latent heat fluxes increase with height from the surface up to ~0.8Zi (where Zi is the convective boundary layer depth) and then decrease to ~0 at Zi. Peak fluxes aloft exceeding 500 W m−2 are associated with periods of increased cumulus cloud cover and stronger jumps in the mean humidity profile. These entrainment fluxes are much larger than the surface fluxes, indicating substantial drying over the 0–0.8Zi layer accompanied by moistening aloft as the CBL deepens over the diurnal cycle. We also show that the boundary layer humidity budget is approximately closed by computing the flux divergence across the 0–0.8Zi layer. Composite subcloud velocity and water vapor anomalies show that clouds are linked to coherent updraft and moisture plumes. The moisture anomaly is Gaussian, most pronounced above 0.8Zi and systematically wider than the velocity anomaly, which has a narrow central updraft flanked by downdrafts. This size and shape disparity results in downdrafts characterized by a high water vapor mixing ratio and thus a broad joint probability density function (JPDF) of velocity and mixing ratio in the upper CBL. We also show that cloud-base latent heat fluxes can be both positive and negative and that the instantaneous positive fluxes can be very large (~10 000 W m−2). However, since cloud fraction tends to be small, the net impact of these fluxes remains modest.

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A water vapor modulated aerosol impact on ice crystal size

10.5194/acp-2017-548 ◽

2017 ◽

Cited By ~ 1

Author(s):

Bin Zhao ◽

Kuo-Nan Liou ◽

Yu Gu ◽

Jonathan H. Jiang ◽

Qinbin Li ◽

...

Keyword(s):

Water Vapor ◽

Radiative Forcing ◽

Deep Convection ◽

Significant Negative Correlation ◽

Formation Mechanisms ◽

Strong Positive Correlation ◽

Ice Crystal ◽

Ice Clouds ◽

Dry Conditions ◽

The Impact

Abstract. The interactions between aerosols and ice clouds represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. In particular, the impact of aerosols on ice crystal effective radius (Rei), which is a key parameter determining ice clouds' net radiative effect, is highly uncertain due to limited and conflicting observational evidence. Here we investigate the effects of aerosols on Rei under different meteorological conditions using 9-year satellite observations. We find that the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters. While there is a significant negative correlation between Rei and aerosol loading in moist conditions, consistent with the Twomey effect for liquid clouds, a strong positive correlation between the two occurs in dry conditions. Simulations based on a cloud parcel model suggest that water vapor modulates the relative importance of different ice nucleation modes, leading to the opposite aerosol impacts between moist and dry conditions. When ice clouds are decomposed into those generated from deep convection and formed in-situ, the water vapor modulation remains in effect for both ice cloud types, although the sensitivities of Rei to aerosols differ noticeably between them due to distinct formation mechanisms. The water vapor modulation can largely explain the difference in the responses of Rei to aerosol loadings in various seasons. A proper representation of the water vapor modulation is essential for an accurate estimate of aerosol-cloud radiative forcing produced by ice clouds.

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Quality assessment of water cycle parameters in REMO by Radar-Lidar synergy

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-8455-2007 ◽

2007 ◽

Vol 7 (3) ◽

pp. 8455-8524

Author(s):

B. Hennemuth ◽

A. Weiss ◽

J. Bösenberg ◽

D. Jacob ◽

H. Linné ◽

...

Keyword(s):

Remote Sensing ◽

Heat Flux ◽

Soil Moisture ◽

Water Content ◽

Water Vapour ◽

Water Cycle ◽

Sensible Heat Flux ◽

Regional Model ◽

Cloud Base ◽

Cloud Radar

Abstract. A comparison study of water cycle parameters derived from ground-based remote-sensing instruments and from the regional model REMO is presented. Observational data sets were collected during three measuring campaigns in summer/autumn 2003 and 2004 at Richard Aßmann Observatory, Lindenberg, Germany. The remote sensing instruments which were used are differential absorption lidar, Doppler lidar, ceilometer, cloud radar, and micro rain radar for the derivation of humidity profiles, ABL height, water vapour flux profiles, cloud parameters, and rain rate. Additionally, surface latent and sensible heat flux and soil moisture were measured. Error ranges and representativity of the data are discussed. For comparisons the regional model REMO was run for all measuring periods with a horizontal resolution of 18 km and 33 vertical levels. Parameter output was every hour. The measured data were transformed to the vertical model grid and averaged in time in order to better fit with gridbox model values. The comparisons show that the atmospheric boundary layer is not adequately simulated, on most days it is too shallow and too moist. This is found to be caused by a wrong partitioning of energy at the surface, particularly a too large latent heat flux. The reason is obviously an overestimation of soil moisture during drying periods by the one-layer scheme in the model. The profiles of water vapour transport within the ABL appear to be realistically simulated. The comparison of cloud cover reveals an underestimation of low-level and mid-level clouds by the model, whereas the comparison of high-level clouds is hampered by the inability of the cloud radar to see cirrus clouds above 10 km. Simulated ABL clouds apparently have a too low cloud base, and the vertical extent is underestimated. The ice water content of clouds agree in model and observation whereas the liquid water content is unsufficiently derived from cloud radar reflectivity in the present study. Rain rates are similar, but the representativeness of both observations and grid box values is low.

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Abundant Precipitation in Qilian Mountains Generated from the Recycled Moisture over the Adjacent Arid Hexi Corridor, Northwest China

Water ◽

10.3390/w13233354 ◽

2021 ◽

Vol 13 (23) ◽

pp. 3354

Author(s):

Zhihua Zhang ◽

Qiudong Zhao ◽

Shiqiang Zhang

Keyword(s):

Water Vapor ◽

Water Cycle ◽

Precipitable Water ◽

Northwest China ◽

Hexi Corridor ◽

Qilian Mountains ◽

Mountain Areas ◽

Reanalysis Dataset ◽

Weather Forecasts ◽

Endorheic Basin

The observed precipitation was suggestive of abundant precipitation in upstream Qilian mountains and low precipitation in the downstream oasis and desert in an endorheic basin. However, precipitation in mountains generated from the recycled moisture over oasis and desert areas has rarely been studied. The climatological patterns of water vapor from 1980 to 2017 in the Qilian Mountain Region (QMR) and Hexi Corridor Region (HCR) were investigated by the European Centre for Medium-Range Weather Forecasts Interim reanalysis dataset and the Modern-Era Retrospective Analysis for Research and Application, Version 2 reanalysis dataset. The results suggest that the precipitable water content decreases from the adjacent to the mountain areas. There are two channels that transport water vapor from the HCR to the QMR in the low troposphere (surface—600 hPa), suggesting that parts of recycled moisture generated from evapotranspiration over the oasis and desert of the HCR is transported to the QMR, contributing to the abundant precipitation in the QMR. This indicates that the transport mechanism is probably because of the “cold and wet island effect” of the cryosphere in QMR. This is likely one of the essential mechanisms of the water cycle in endorheic river basins, which has rarely been reported.

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Value addition in district level dynamical forecast during monsoon depressions and storms

MAUSAM ◽

10.54302/mausam.v58i1.1094 ◽

2021 ◽

Vol 58 (1) ◽

pp. 1-8

Author(s):

O. P. SINGH ◽

B. LAL ◽

ONKARI PRASAD

Keyword(s):

Sea Level ◽

Heavy Rainfall ◽

Rainfall Amount ◽

District Level ◽

Value Addition ◽

Maximum Rainfall ◽

Mean Sea Level ◽

Weather Forecasts ◽

Medium Range ◽

Monsoon Depressions

ABSTRACT. The trials of district level forecasts yielded encouraging results during 2005 monsoon. The purpose of this paper is to document the methodology followed in the value addition during the periods of monsoon depressions and storms. The focus is on the use of Mean Sea Level (MSL) positions and the 850 hPa circulation features predicted by different model centres, especially the European Centre for Medium-Range Weather Forecasts (ECMWF). The ECMWF-predicted 72 hr MSL position of the monsoon depression centre was found to be significantly correlated to the actual position of the system and the central location of the realized rainfall zone associated with the system. Even the predicted location of the system at 850 hPa by the ECMWF has been found useful in identifying the districts that received heaviest rainfall associated with the monsoon systems.MM5 and T-80 – predicted locations of the system at 850 hPa yielded lower correlations with the location of the actual rainfall zone associated with the system. As ECMWF – predicted rainfall was not available the rainfall predicted by MM5 and T-80 were used in the computations of the correlations with actual rainfall amounts associated with monsoon depressions and storms. The correlations between MM5 and T-80 – predicted average and maximum rainfall associated with systems and corresponding actual were poor. Though it is not difficult to identify the districts that are likely to be affected by the heavy rainfall associated with monsoon depressions/storms, the prediction of exact rainfall amount for each district (beyond heavy, very heavy or exceptionally heavy categories) is difficult from the model outputs which makes such forecasts a very challenging task. Therefore, the value addition using other inputs such as satellite information, synoptic charts, climatology etc. are very useful in the prediction of rainfall amounts associated with monsoon systems.

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Individual Rainfall Change Based on Observed Hourly Precipitation Records on the Chinese Loess Plateau from 1983 to 2012

Water ◽

10.3390/w12082268 ◽

2020 ◽

Vol 12 (8) ◽

pp. 2268

Author(s):

Wenbin Ding ◽

Fei Wang ◽

Kai Jin ◽

Jianqiao Han ◽

Qiang Yu ◽

...

Keyword(s):

Loess Plateau ◽

Heavy Rainfall ◽

Rainfall Intensity ◽

Rainfall Amount ◽

The Loess Plateau ◽

Total Rainfall ◽

Rainfall Events ◽

Rainfall Duration ◽

Rainfall Frequency ◽

Annual Total

The magnitude and spatiotemporal distribution of precipitation are the main drivers of hydrologic and agricultural processes in soil moisture, runoff generation, soil erosion, vegetation growth and agriculture activities on the Loess Plateau (LP). This study detects the spatiotemporal variations of individual rainfall events during a rainy season (RS) from May to September based on the hourly precipitation data measured at 87 stations on the LP from 1983 to 2012. The incidence and contribution rates were calculated for all classes of rainfall duration and intensity to identify the dominant contribution to the rainfall amount and frequency variations. The trend rates of regional mean annual total rainfall amount (ATR) and annual mean rainfall intensity (ARI) were 0.43 mm/year and 0.002 mm/h/year in the RS for 1983–2012, respectively. However, the regional mean annual total rainfall frequency (ARF) and rainfall events (ATE) were −0.27 h/year and −0.11 times/year, respectively. In terms of spatial patterns, an increase in ATR appeared in most areas except for the southwest, while the ARI increased throughout the study region, with particularly higher values in the northwest and southeast. Areas of decreasing ARF occurred mainly in the northwest and central south of the LP, while ATE was found in most areas except for the northeast. Short-duration (≤6 h) and light rainfall events occurred mostly on the LP, accounting for 69.89% and 72.48% of total rainfall events, respectively. Long-duration (≥7 h) and moderate rainfall events contributed to the total rainfall amount by 70.64% and 66.73% of the total rainfall amount, respectively. Rainfall frequency contributed the most to the variations of rainfall amount for light and moderate rainfall events, while rainfall intensity played an important role in heavy rainfall and rainstorms. The variation in rainfall frequency for moderate rainfall, heavy rainfall, and rainstorms is mainly affected by rainfall duration, while rainfall event was identified as a critical factor for light rainfall. The characteristics in rainfall variations on the Loess Plateau revealed in this study can provide useful information for sustainable water resources management and plans.

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