Coupling of Precipitation and Cloud Structures in Oceanic Extratropical Cyclones to Large-Scale Moisture Flux Convergence

Precipitation (from TMPA) and cloud structures (from MODIS) in extratropical cyclones (ETCs) are modulated by phases of large-scale moisture flux convergence (from MERRA-2) in the sectors of ETCs, which are studied in a new coordinate system with directions of both surface warm fronts (WFs) and surface cold fronts (CFs) fixed. The phase of moisture flux convergence is described by moisture dynamical convergence Qcnvg and moisture advection Qadvt. Precipitation and occurrence frequencies of deep convective clouds are sensitive to changes in Qcnvg, while moisture tendency is sensitive to changes in Qadvt. Increasing Qcnvg and Qadvt during the advance of the WF is associated with increasing occurrences of both deep convective and high-level stratiform clouds. A rapid decrease in Qadvt with a relatively steady Qcnvg during the advance of the CF is associated with high-level cloud distribution weighting toward deep convective clouds. Behind the CF (cold sector or area with polar air intrusion), the moisture flux is divergent with abundant low- and midlevel clouds. From deepening to decaying stages, the pre-WF and WF sectors experience high-level clouds shifting to more convective and less stratiform because of decreasing Qadvt with relatively steady Qcnvg, and the CF experiences shifting from high-level to midlevel clouds. Sectors of moisture flux divergence are less influenced by cyclone evolution. Surface evaporation is the largest in the cold sector and the CF during the deepening stage. Deepening cyclones are more efficient in poleward transport of water vapor.

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A CloudSat–CALIPSO View of Cloud and Precipitation Properties across Cold Fronts over the Global Oceans

Journal of Climate ◽

10.1175/jcli-d-15-0052.1 ◽

2015 ◽

Vol 28 (17) ◽

pp. 6743-6762 ◽

Cited By ~ 24

Author(s):

Catherine M. Naud ◽

Derek J. Posselt ◽

Susan C. van den Heever

Keyword(s):

Large Scale ◽

Cold Front ◽

Conveyor Belt ◽

Low Level ◽

Scale Parameters ◽

Convective Clouds ◽

Cold Fronts ◽

Surface Front ◽

High Level ◽

The Impact

Abstract The distribution of cloud and precipitation properties across oceanic extratropical cyclone cold fronts is examined using four years of combined CloudSat radar and CALIPSO lidar retrievals. The global annual mean cloud and precipitation distributions show that low-level clouds are ubiquitous in the postfrontal zone while higher-level cloud frequency and precipitation peak in the warm sector along the surface front. Increases in temperature and moisture within the cold front region are associated with larger high-level but lower mid-/low-level cloud frequencies and precipitation decreases in the cold sector. This behavior seems to be related to a shift from stratiform to convective clouds and precipitation. Stronger ascent in the warm conveyor belt tends to enhance cloudiness and precipitation across the cold front. A strong temperature contrast between the warm and cold sectors also encourages greater post-cold-frontal cloud occurrence. While the seasonal contrasts in environmental temperature, moisture, and ascent strength are enough to explain most of the variations in cloud and precipitation across cold fronts in both hemispheres, they do not fully explain the differences between Northern and Southern Hemisphere cold fronts. These differences are better explained when the impact of the contrast in temperature across the cold front is also considered. In addition, these large-scale parameters do not explain the relatively large frequency in springtime postfrontal precipitation.

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Climatological Behavior of Precipitating Clouds in the Northeast Region of Brazil

Advances in Meteorology ◽

10.1155/2017/5916150 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 10

Author(s):

Rayana Santos Araújo Palharini ◽

Daniel Alejandro Vila

Keyword(s):

Relative Frequency ◽

Tropical Rainfall Measuring Mission ◽

Precipitation Radar ◽

Convective Clouds ◽

Strong Signal ◽

Deep Convective Clouds ◽

Stratiform Clouds ◽

Precipitating Clouds ◽

Data Period

This study aims to analyze the climatological classification of precipitating clouds in the Northeast of Brazil using the radar on board the Tropical Rainfall Measuring Mission (TRMM) satellite. Thus, for this research a time series of 15 years of satellite data (period 1998–2012) was analyzed in order to identify what types of clouds produce precipitation estimated by Precipitation Radar (PR) and how often these clouds occur. From the results of this work it was possible to estimate the average relative frequency of each type of cloud present in weather systems that influence the Northeast of Brazil. In general, the stratiform clouds and shallow convective clouds are the most frequent in this region, but the associated rainfall is not as abundant as precipitation caused by deep convective clouds. It is also seen that a strong signal of shallow convective clouds modulates rainfall over the coastal areas of Northeast of Brazil and adjacent ocean. In this scenario, the main objective of this study is to contribute to a better understanding of the patterns of cloud types associated with precipitation and building a climatological analysis from the classification of clouds.

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Variations in the Summertime Atmospheric Hydrologic Cycle Associated with Seasonal Precipitation Anomalies over the Southwestern United States

Journal of Hydrometeorology ◽

10.1175/jhm521.1 ◽

2006 ◽

Vol 7 (4) ◽

pp. 788-807 ◽

Cited By ~ 4

Author(s):

Bruce T. Anderson ◽

Hideki Kanamaru ◽

John O. Roads

Keyword(s):

New Mexico ◽

Large Scale ◽

Moisture Flux ◽

Hydrologic Cycle ◽

Seasonal Precipitation ◽

Model Simulations ◽

Moisture Flux Convergence ◽

Rainfall Season ◽

Rainfall Anomalies ◽

The Mean

Abstract This paper examines year-to-year variations in the large-scale summertime hydrologic cycle over the southwestern United States using a suite of regional model simulations and surface- and upper-air-based observations. In agreement with previous results, it is found that observed interannual precipitation variations in this region can be subdivided into two spatiotemporal regimes—one associated with rainfall variability over the southwestern portion of the domain centered on Arizona and the other associated with variations over the southeastern portion centered on western Texas and eastern New Mexico. Because of the limited duration of the model simulation data, it is possible to only investigate one positive rainfall season over the Arizona region and one negative rainfall season over the New Mexico region. From these investigations it appears that for the positive rainfall anomalies over Arizona excess seasonal precipitation is balanced by both enhanced evaporation and vertically integrated large-scale moisture flux convergence. Vertical profiles of these terms indicate that the anomalous large-scale moisture flux convergence is actually related to a decrease in the mean large-scale moisture flux divergence aloft; below 800 mb there is a decrease in the mean moisture flux convergence typically found at these levels, which in turn produces anomalous moisture divergence from the region. For the negative rainfall anomalies over New Mexico similar results, but of opposite sign, are found; one exception is that at the lowest levels there is an additional (negative) contribution to the vertically integrated moisture flux convergence anomaly related to a weakening of the mean low-level moisture flux convergence during the low-rainfall year. Further studies using two different model simulations with the same large-scale dynamic forcing but differing initial soil moisture values indicate that similar balances are also found for rainfall anomalies related to surface soil moisture changes within the domain, suggesting that the changes in large-scale moisture flux convergence described above can be attributed to both year-to-year variations in the regional land–atmosphere interactions as well as variations in the large-scale circulation patterns.

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Sensitivity of a Large Ensemble of Tropical Convective Systems to Changes in the Thermodynamic and Dynamic Forcings

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2446.1 ◽

2008 ◽

Vol 65 (6) ◽

pp. 1773-1794 ◽

Cited By ~ 7

Author(s):

Zachary A. Eitzen ◽

Kuan-Man Xu

Keyword(s):

Radiative Forcing ◽

Large Scale ◽

Radiant Energy ◽

Convective Cloud ◽

Energy System ◽

Scale Model ◽

Convective Clouds ◽

Cloud Properties ◽

Deep Convective Clouds ◽

Deep Convective Cloud

Abstract A two-dimensional cloud-resolving model (CRM) is used to perform five sets of simulations of 68 deep convective cloud objects identified with Clouds and the Earth’s Radiant Energy System (CERES) data to examine their sensitivity to changes in thermodynamic and dynamic forcings. The control set of simulations uses observed sea surface temperatures (SSTs) and is forced by advective cooling and moistening tendencies derived from a large-scale model analysis matched to the time and location of each cloud object. Cloud properties, such as albedo, effective cloud height, cloud ice and snow path, and cloud radiative forcing (CRF), are analyzed in terms of their frequency distributions rather than their mean values. Two sets of simulations, F+50% and F−50%, use advective tendencies that are 50% greater and 50% smaller than the control tendencies, respectively. The increased cooling and moistening tendencies cause more widespread convection in the F+50% set of simulations, resulting in clouds that are optically thicker and higher than those produced by the control and F−50% sets of simulations. The magnitudes of both longwave and shortwave CRF are skewed toward higher values with the increase in advective forcing. These significant changes in overall cloud properties are associated with a substantial increase in deep convective cloud fraction (from 0.13 for the F−50% simulations to 0.34 for the F+50% simulations) and changes in the properties of non–deep convective clouds, rather than with changes in the properties of deep convective clouds. Two other sets of simulations, SST+2K and SST−2K, use SSTs that are 2 K higher and 2 K lower than those observed, respectively. The updrafts in the SST+2K simulations tend to be slightly stronger than those of the control and SST−2K simulations, which may cause the SST+2K cloud tops to be higher. The changes in cloud properties, though smaller than those due to changes in the dynamic forcings, occur in both deep convective and non–deep convective cloud categories. The overall changes in some cloud properties are moderately significant when the SST is changed by 4 K. The changes in the domain-averaged shortwave and longwave CRFs are larger in the dynamic forcing sensitivity sets than in the SST sensitivity sets. The cloud feedback effects estimated from the SST−2K and SST+2K sets are comparable to prior studies.

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Influence of mid-latitude oceanic fronts on the atmospheric water cycle

10.5194/egusphere-egu2020-10022 ◽

2020 ◽

Author(s):

Fumiaki Ogawa ◽

Thomas Spengler

Keyword(s):

Heat Exchange ◽

Large Scale ◽

Water Cycle ◽

Moisture Flux ◽

Convective Precipitation ◽

Atmospheric Water ◽

Moisture Flux Convergence ◽

Sst Front ◽

Oceanic Fronts ◽

Sst Fronts

&#160;&#160;&#160;&#160;&#160; Midlatitude oceanic fronts play an important role in the air-sea coupled weather and climate system. Created by the confluence of warm and cool oceanic western boundary currents, the strong sea-surface temperature (SST) gradient is maintained throughout the year. The climatological mean turbulent air-sea heat exchange maximizes along these SST fronts and collocates with the major atmospheric storm tracks. A recent study identified that the air-sea heat exchange along the SST front mainly occurs on sub-weekly time scales, associated with synoptic atmospheric disturbances. This implies a crucial role of air-sea moisture exchange along the SST fronts on the atmospheric water cycle through the intensification of atmospheric cyclones and the associated precipitation.&#160;&#160;&#160;&#160;&#160;&#160;&#160; In this study, we investigate this influence of the SST front on the atmospheric water cycle by analyzing the atmospheric response to different prescribed SST in the Atmospheric general circulation model For the Earth Simulator (AFES). Changing the latitude of the prescribed zonally symmetric SST in aqua-planet configuration, we find a distinctive response in convective and large-scale precipitation, surface latent and sensible heat fluxes, as well as diabatic heating and moistening with respect to the latitude of SST front. Upward surface latent heat flux and convective precipitation always maximize along the equatorward flank of SST front. On the other hand, large-scale precipitation is always located on the poleward flank of the SST front, in correspondence with the maximum atmospheric moisture flux convergence. The moisture flux convergence is mainly associated with midlatitude eddies and not with the time mean transport. This highlights the influence of mid-latitude SST fronts on the atmospheric water cycle through the organization of atmospheric storm track.

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MJO Moisture Budget during DYNAMO in a Cloud-Resolving Model

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0379.1 ◽

2016 ◽

Vol 73 (6) ◽

pp. 2257-2278 ◽

Cited By ~ 24

Author(s):

Matthew A. Janiga ◽

Chidong Zhang

Keyword(s):

Large Scale ◽

Moisture Gradient ◽

Moisture Budget ◽

Physical Processes ◽

Low Level ◽

Moisture Advection ◽

Stratiform Clouds ◽

Cloud Resolving Model ◽

Eddy Transport ◽

Upper Level

Abstract Contributions by different physical processes and cloud types to the sum of the large-scale vertical moisture advection and apparent moisture sink observed by the DYNAMO field campaign northern sounding array during the passage of a Madden–Julian oscillation (MJO) event are estimated using a cloud-resolving model. The sum of these two moisture budget terms is referred to as the column-confined moisture tendency MC. Assuming diabatic balance, the contribution of different physical processes and cloud types to the large-scale vertical velocity and MC can be estimated using simulated diabatic tendencies and the domain-averaged static stability and vertical moisture gradient. Low-level moistening preceding MJO passage is captured by MC and dominated by the effects of shallow clouds. Because of the large vertical moisture gradient at this level, condensational heating in these clouds generates ascent and vertical moisture advection overwhelming the removal of water vapor by condensation. Shallow convective eddy transport also contributes to low-level moistening during this period. Eddy transport by congestus and deep convective clouds contributes to subsequent mid- and upper-level moistening, respectively, as well as low-level drying. Because the upper-level vertical moisture gradient is small, ice deposition within stratiform clouds has a net drying effect. The weak eddy transport in stratiform clouds is unable to compensate for this drying. Nonprecipitating clouds mainly modulate MC through their effects on radiation. During the enhanced phase, reduced longwave cooling results in less subsidence and drying; the opposite occurs during the suppressed phase. Large-scale horizontal advection, which is not included in MC, is responsible for much of the drying during the dissipating phase.

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Estimating the Influence of Evaporation and Moisture-Flux Convergence upon Seasonal Precipitation Rates. Part II: An Analysis for North America Based upon the NCEP–DOE Reanalysis II Model

Journal of Hydrometeorology ◽

10.1175/2009jhm1063.1 ◽

2009 ◽

Vol 10 (4) ◽

pp. 893-911 ◽

Cited By ~ 12

Author(s):

Bruce T. Anderson ◽

Alex C. Ruane ◽

John O. Roads ◽

Masao Kanamitsu

Keyword(s):

Large Scale ◽

Moisture Flux ◽

Early Summer ◽

Monsoon Circulation ◽

Atmospheric Moisture ◽

Storm Activity ◽

Moisture Flux Convergence ◽

Low Level ◽

Low Level Jet ◽

Northwestern Mexico

Abstract In this paper, a diagnostic metric—termed the local-convergence ratio—is used to analyze the contribution of evaporation and atmospheric moisture-flux convergence to model-based estimates of climatological precipitation over the North American continent. Generally, the fractional evaporative contribution is largest during spring and summer when evaporation is largest and decreases as evaporation decreases. However, there appears to be at least three regions with distinct spatiotemporal seasonal evolutions of this ratio. Over both the northern and western portions of the continent, the fractional evaporative contribution peaks in spring and early summer and decreases during fall and into winter. Over the northern portion, this fall decrease is related to an increase in atmospheric moisture-flux convergence associated with enhanced meridional moisture fluxes into the region; over the western coastal regions, the fall decrease in evaporative contribution is associated with a decrease in evaporation and an increase in total moisture-flux convergence, most likely associated with increased storm activity. In contrast, over the central portions of the continent, the fractional evaporative contribution to precipitation remains relatively low in spring—when enhanced low-level jet activity increases the low-level atmospheric moisture flux convergence into the region—and instead peaks in summer and fall—when the moisture-flux convergence associated with the low-level jet decreases and precipitation is balanced predominantly by local evaporation. Finally, over the southwestern United States and northwestern Mexico, the fractional evaporative contribution to precipitation is found to contain a wintertime minimum as well as a secondary minimum during summer. This latter feature is due to a substantial increase in low-level atmospheric moisture-flux convergence associated with the large-scale monsoon circulation that influences this region during this time.

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Comparative study of atmospheric water vapor budget associated with precipitation in Central US and eastern Mediterranean

Advances in Geosciences ◽

10.5194/adgeo-23-3-2010 ◽

2010 ◽

Vol 23 ◽

pp. 3-9 ◽

Cited By ~ 4

Author(s):

A. Zangvil ◽

P. J. Lamb ◽

D. H. Portis ◽

F. Jin ◽

S. Malka

Keyword(s):

Water Vapor ◽

Comparative Study ◽

Large Scale ◽

Eastern Mediterranean ◽

Precipitable Water ◽

Moisture Flux ◽

Flux Divergence ◽

Pronounced Difference ◽

The Us ◽

Water Vapor Budget

Abstract. Water vapor budget (WVB) analysis is a powerful tool for studying processes leading to precipitation (P), since the linkages among atmospheric dynamics, water vapor fields, surface conditions, and P are constrained by the moisture continuity equation. This paper compares WVB calculations over the US Midwest (MW), the US Southern Great Plains (SGP), and the eastern Mediterranean Sea (EM) during their seasons of maximum P. Despite the inter-regional differences in time of year, size of region, and surface characteristics, the WVBs over these regions have common features. First, the change in precipitable water (dPW) is highly correlated with the moisture flux divergence (MFD) and not evaporation (E), implying that atmospheric humidity is affected more by the large-scale atmospheric circulation than land-atmosphere interactions. Second, P is positively correlated with moisture inflow (IF/A). However, a pronounced difference exists between the North American and the Mediterranean study regions with respect to the processes associated with increased P. For the MW and the SGP, increased P is associated with moisture flux convergence (−MFD) due to increased IF/A. In contrast, increased P over the EM is not associated with −MFD, since both the outflow (OF/A) and IF/A increase at similar rates. Recycling ratio (R) estimates were calculated for each region using an equation previously developed. The moisture recycling methodology involves the externally advected versus locally evaporated contributions to P being expressed in terms of a "bulk" formulation in which IF/A and OF/A are defined at the boundaries of the study area. Due to its scale dependence, R cannot be directly compared among the different regions, and a normalization procedure was developed for this comparative study. Its results suggest the normalized R ranges between 12-25% for the study regions, with the value for the oceanic EM being somewhat larger than over the continental MW and SGP.

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New MESSy scavenging subroutine to treat aerosol particles gas-phase partitioning in convective clouds

10.5194/egusphere-egu21-1361 ◽

2021 ◽

Author(s):

Giorgio Taverna ◽

Marc Barra ◽

Holger Tost

Keyword(s):

Liquid Phase ◽

Gas Phase ◽

Aerosol Particles ◽

Phase Partitioning ◽

Convective Clouds ◽

Terrestrial Atmosphere ◽

Deep Convective Clouds ◽

High Level

The Modular Earth Submodel System (MESSy) has been proven to be successful in the understanding of several processes which characterize the terrestrial atmosphere and climate.However, the complexity of aerosol particles/gas phase partitioning of species in deep convective clouds together with the inherent problems of modelling sub-grid scale processes, make MESSy results significant underestimated, especially in case of SO2, when compared with available flight observations. For this reason, the subroutine which reproduce the scavenging of these species has been updated to include a more realistic treatment of liquid/phase partitioning of aerosol induced species in high level clouds.Results obtained are shown in this poster.

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Drivers and physical processes of drought events over the State of São Paulo, Brazil

Climate Dynamics ◽

10.1007/s00382-021-06091-2 ◽

2022 ◽

Author(s):

Abayomi A. Abatan ◽

Simon F. B. Tett ◽

Buwen Dong ◽

Christopher Cunningham ◽

Conrado M. Rudorff ◽

...

Keyword(s):

Large Scale ◽

Model Simulation ◽

Moisture Flux ◽

Sao Paulo ◽

The State ◽

Climatic Research Unit ◽

Summer Drought ◽

São Paulo ◽

Physical Processes ◽

Moisture Flux Convergence

AbstractThe State of São Paulo, Brazil (SSP) was impacted by severe water shortages during the intense austral summer drought of 2013/2014 and 2014/2015 (1415SD). This study seeks to understand the features and physical processes associated with these summer droughts in the context of other droughts over the region during 1961–2010. Thus, this study examines the spatio-temporal characteristics of anomalously low precipitation over SSP and the associated large-scale dynamics at seasonal timescales, using an observation-based dataset from the Climatic Research Unit (CRU) and model simulation outputs from the Met Office Hadley Centre Global Environment Model (HadGEM3-GA6 at N216 resolution). The study analyzes Historical and Natural simulations from the model to examine the role of human-induced climate forcing on droughts over SSP. Composites of large-scale fields associated with droughts are derived from ERA-20C and ERA-Interim reanalysis and the model simulations. HadGEM3-GA6 simulations capture the observed interannual variability of normalized precipitation anomalies over SSP, but with biases. Drought events over SSP are related to subsidence over the region. This is associated with reduced atmospheric moisture over the region as indicated by the analysis of the vertically integrated moisture flux convergence, which is dominated by reduced moisture flux convergence. The Historical simulations simulate the subsidence associated with droughts, but there are magnitude and location biases. The similarities between the circulation features of the severe 1415SD and other drought events over the region show that understanding of the dynamics of the past drought events over SSP could guide assessment of changes in risk of future droughts and improvements of model performance. The study highlights the merits and limitations of the HadGEM3-GA6 simulations. The model possesses the skills in simulating the large-scale atmospheric circulations modulating precipitation variability, leading to drought conditions over SSP.

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