A New Metric for Estimating the Influence of Evaporation on Seasonal Precipitation Rates

2008 ◽  
Vol 9 (3) ◽  
pp. 576-588 ◽  
Author(s):  
Bruce T. Anderson ◽  
Guido Salvucci ◽  
Alex C. Ruane ◽  
John O. Roads ◽  
Masao Kanamitsu
Keyword(s):  
Local Convergence ◽  
Large Scale ◽  
Precipitable Water ◽  
Moisture Flux ◽  
Seasonal Precipitation ◽  
Atmospheric Moisture ◽  
Moisture Recycling ◽  
Consistent Model ◽  
Self Consistent ◽  
Precipitation Recycling

Abstract The objective of this paper is to introduce a diagnostic metric—termed the local-convergence ratio—that can be used to quantify the contribution of evaporation (and transpiration) to the atmospheric hydrologic cycle, and precipitation in particular, over a given region. Previous research into regional moisture (or precipitation) recycling has produced numerous methods for estimating the contributions of “local” (i.e., evaporated) moisture to climatological precipitation and its variations. In general, these metrics quantify the evaporative contribution to the mass of precipitable water within an atmospheric column by comparing the vertically integrated atmospheric fluxes of moisture across a region with the fluxes via evaporation. Here a new metric is proposed, based on the atmospheric moisture tendency equation, which quantifies the evaporative contribution to the rate of precipitation by comparing evaporative convergence into the column with large-scale moisture-flux convergence. Using self-consistent, model-derived estimates of the moisture-flux fields and the atmospheric moisture tendency terms, the authors compare estimates of the flux-based moisture-recycling ratio with the newly introduced local-convergence ratio. Differences between the two ratios indicate that they can be considered complementary, but independent, descriptors of the atmospheric hydroclimatology for a given region.

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

2006 ◽  
Vol 7 (4) ◽  
pp. 788-807 ◽  
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.

scholarly journals Deep rotating convection generates the polar hexagon on Saturn

2020 ◽  
Vol 117 (25) ◽  
pp. 13991-13996 ◽  
Author(s):  
Rakesh K. Yadav ◽  
Jeremy Bloxham
Keyword(s):  
Flow Pattern ◽  
High Latitude ◽  
Large Scale ◽  
Three Dimensional ◽  
Giant Planets ◽  
Zonal Flows ◽  
Self Organized ◽  
Consistent Model ◽  
Self Consistent ◽  
Polygonal Pattern

Numerous land- and space-based observations have established that Saturn has a persistent hexagonal flow pattern near its north pole. While observations abound, the physics behind its formation is still uncertain. Although several phenomenological models have been able to reproduce this feature, a self-consistent model for how such a large-scale polygonal jet forms in the highly turbulent atmosphere of Saturn is lacking. Here, we present a three-dimensional (3D) fully nonlinear anelastic simulation of deep thermal convection in the outer layers of gas giant planets that spontaneously generates giant polar cyclones, fierce alternating zonal flows, and a high-latitude eastward jet with a polygonal pattern. The analysis of the simulation suggests that self-organized turbulence in the form of giant vortices pinches the eastward jet, forming polygonal shapes. We argue that a similar mechanism is responsible for exciting Saturn’s hexagonal flow pattern.

scholarly journals 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

2009 ◽  
Vol 10 (4) ◽  
pp. 893-911 ◽  
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.

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

2010 ◽  
Vol 23 ◽  
pp. 3-9 ◽  
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.

THEORY AND SELF-CONSISTENT MODEL OF DUST-DRIVEN WINDS

2002 ◽  
Vol 5 ◽  
pp. 65-65
Author(s):  
S. Liberatore ◽  
J.-P.J. Lafon ◽  
N. Berruyer
Keyword(s):  
Consistent Model ◽  
Self Consistent

scholarly journals Stellar Flares: Observations and Theory

1989 ◽  
Vol 104 (2) ◽  
pp. 49-52
Author(s):  
Suzanne L. Hawley
Keyword(s):  
Scaling Law ◽  
Dynamic Scaling ◽  
X Ray ◽  
Temperature Distributions ◽  
Photometric And Spectroscopic Observations ◽  
Stellar Flares ◽  
Consistent Model ◽  
Self Consistent ◽  
Flare Model ◽  
Large Flare

AbstractPhotometric and spectroscopic observations of a very large flare on AD Leo are presented. A self consistent model of a flare corona, transition region and chromosphere is developed; in particular the chromospheric temperature distributions resulting from X-ray and EUV irradiation by coronae of various temperatures are determined. The predicted line fluxes in Hγ are compared to the observed line fluxes to find the coronal temperature as a function of time during the flare. This run of temperature with time is then compared with the predictions of an independent theoretical flare model based on a dynamic scaling law (see paper by Fisher and Hawley, these proceedings).

scholarly journals A Self‐Consistent Model for Sorption and Transport in Polyimide‐Derived Carbon Molecular Sieve Gas Separation Membranes

2020 ◽  
Vol 132 (46) ◽  
pp. 20523-20527
Author(s):  
Oishi Sanyal ◽  
Samuel S. Hays ◽  
Nicholas E. León ◽  
Yoseph A. Guta ◽  
Arun K. Itta ◽  
...  
Keyword(s):  
Gas Separation ◽  
Molecular Sieve ◽  
Carbon Molecular Sieve ◽  
Separation Membranes ◽  
Gas Separation Membranes ◽  
Consistent Model ◽  
Self Consistent
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