scholarly journals Characteristics of a Hailstorm over the Andean La Paz Valley

2019 ◽  
Author(s):  
Marcelo Zamuriano ◽  
Andrey Martynov ◽  
Luca Panziera ◽  
Stefan Brönnimann
Keyword(s):  
Deep Convection ◽  
Local Features ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Lake Breeze ◽  
Shallow Convection ◽  
La Paz ◽  
Surface Heat Fluxes ◽  
Cold Pools ◽  
Lake Temperature

Abstract. The iconic hailstorm and flash flood episode of 19 February 2002 over La Paz city is numerically investigated in this article. Large scale atmospheric circulation is dynamically downscaled in order to take into account the complex orography forcing and local features. Satellite observations suggests late morning shallow convection over the Altiplano that becomes deep convection in the early afternoon around complex orography. The control simulation captures well the cloud evolution and suggest a two-stage precipitation mechanism. First, early convection occurred around 1200 LST and originated from thermodynamic instability combined with lake breeze and orographic lifting. Rainfall discharge then generated cold pools. During the second stage, cold pools around complex orography were propagated by lake breeze and encountered the La Paz Valley breeze, triggering the deep convection near La Paz city around 1400 LST. We assess the importance of local features through numerical experiments, which include modification of orography, suppression of surface heat fluxes, changes of surface lake temperature and removal of the lake. We show the importance of orographic configuration as triggering mechanism for convection initiation and for mesoscale circulation, the role of lake temperature for frontal breeze and propagation of cold pools, and of surface heat fluxes for atmospheric instability. This study highlights the complex interaction between lakes, surface heating and orography that favour deep convection and hailstorm formation, which is especially relevant around the Titicaca lake region.

Two- and Three-Dimensional Cloud-Resolving Model Simulations of the Mesoscale Enhancement of Surface Heat Fluxes by Precipitating Deep Convection

2006 ◽  
Vol 19 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Xiaoqing Wu ◽  
Stephen Guimond
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Deep Convection ◽  
Three Dimensional ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Total Flux ◽  
Surface Heat Fluxes ◽  
Cloud Resolving Model ◽  
2D And 3D

Abstract Two-dimensional (2D) and three-dimensional (3D) cloud-resolving model (CRM) simulations are conducted to quantify the enhancement of surface sensible and latent heat fluxes by tropical precipitating cloud systems for 20 days (10–30 December 1992) during the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). The mesoscale enhancement appears to be analogous across both 2D and 3D CRMs, with the enhancement for the sensible heat flux accounting for 17% of the total flux for each model and the enhancement for the latent heat flux representing 18% and 16% of the total flux for 2D and 3D CRMs, respectively. The convection-induced gustiness is mainly responsible for the enhancement observed in each model simulation. The parameterization schemes of the mesoscale enhancement by the gustiness in terms of convective updraft, downdraft, and precipitation, respectively, are examined using each version of the CRM. The scheme utilizing the precipitation was found to yield the most desirable estimations of the mean fluxes with the smallest rms error. The results together with previous findings from other studies suggest that the mesoscale enhancement of surface heat fluxes by the precipitating deep convection is a subgrid process apparent across various CRMs and is imperative to incorporate into general circulation models (GCMs) for improved climate simulation.

scholarly journals Role of surface heat fluxes underneath cold pools

2016 ◽  
Vol 43 (2) ◽  
pp. 874-883 ◽  
Author(s):  
Pierre Gentine ◽  
Alix Garelli ◽  
Seung‐Bu Park ◽  
Ji Nie ◽  
Giuseppe Torri ◽  
...  
Keyword(s):  
Surface Heat ◽  
Heat Fluxes ◽  
Surface Heat Fluxes ◽  
Cold Pools

scholarly journals Deep water formation in the North Atlantic Ocean in high resolution global coupled climate models

2020 ◽  
Author(s):  
Torben Koenigk ◽  
Ramon Fuentes-Franco ◽  
Virna Meccia ◽  
Oliver Gutjahr ◽  
Laura C. Jackson ◽  
...  
Keyword(s):  
High Resolution ◽  
Climate Models ◽  
Deep Convection ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Labrador Sea ◽  
Greenland Sea ◽  
Surface Heat Fluxes ◽  
The North ◽  
Coupled Climate Models

Abstract. Simulations from seven global coupled climate models performed at high and standard resolution as part of the High Resolution Model Intercomparison Project (HighResMIP) have been analyzed to study the impact of horizontal resolution in both ocean and atmosphere on deep ocean convection in the North Atlantic and to evaluate the robustness of the signal across models. The representation of convection varies strongly among models. Compared to observations from ARGO-floats, most models substantially overestimate deep water formation in the Labrador Sea. In the Greenland Sea, some models overestimate convection while others show too weak convection. In most models, higher ocean resolution leads to increased deep convection in the Labrador Sea and reduced convection in the Greenland Sea. Increasing the atmospheric resolution has only little effect on the deep convection, except in two models, which share the same atmospheric component and show reduced convection. Simulated convection in the Labrador Sea is largely governed by the release of heat from the ocean to the atmosphere. Higher resolution models show stronger surface heat fluxes than the standard resolution models in the convection areas, which promotes the stronger convection in the Labrador Sea. In the Greenland Sea, the connection between high resolution and ocean heat release to the atmosphere is less robust and there is more variation across models in the relation between surface heat fluxes and convection. Simulated freshwater fluxes have less impact than surface heat fluxes on convection in both the Greenland and Labrador Sea and this result is insensitive to model resolution. is not robust across models. The mean strength of the Labrador Sea convection is important for the mean Atlantic Meridional Overturning Circulation (AMOC) and in around half of the models the variability of Labrador Sea convection is a significant contributor to the variability of the AMOC.

scholarly journals Shallow-to-Deep Transition of Continental Moist Convection: Cold Pools, Surface Fluxes, and Mesoscale Organization

2018 ◽  
Vol 75 (12) ◽  
pp. 4071-4090 ◽  
Author(s):  
Marcin J. Kurowski ◽  
Kay Suselj ◽  
Wojciech W. Grabowski ◽  
Joao Teixeira
Keyword(s):  
Surface Heat ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Cloud Base ◽  
Moist Convection ◽  
Near Surface ◽  
Surface Heat Fluxes ◽  
Cold Pools ◽  
Interactive Surface ◽  
Convection Parameterization

Abstract Large-eddy simulation is used to investigate the effects of cold pools driven by rain evaporation on the shallow-to-deep convection transition over land. The physically consistent methodologies are developed to obtain a time-dependent reference ensemble without cold pools and to apply interactive surface heat fluxes without modeling of surface energy and water budgets. Three different simulation ensembles are contrasted. The reference ensemble, in the spirit of one-dimensional single-column models, eliminates cold pools by horizontally homogenizing negative buoyancy production due to rain evaporation. The additional ensembles complement the reference cold-pool-free ensemble by including cold pools and by applying either interactive or prescribed surface fluxes. Contrasting these ensembles suggests possible improvements of convection parameterization in large-scale models of weather and climate. Without cold pools, the reference ensemble preserves key features of buoyancy-driven cellular convection associated with a field of convective plumes, as assumed in a typical convection parameterization. With cold pools, a significant enhancement of surface heat and moisture fluxes and about an hour delay of their daily maximum is simulated. Cold pools enhance near-surface temperature and moisture standard deviations as well as maxima of the near-surface updraft velocity. They also lead to the reduction of cloud lateral entrainment, deeper vertical development of the cloud layer, and a few-times-larger accumulated surface precipitation. Interactive surface fluxes provide a damping mechanism that noticeably suppresses all these effects. Perhaps surprisingly, cold pools do not significantly change the cloud-base convective mass flux that approximately follows the evolution of surface heat fluxes.

Trends of land surface heat fluxes on the Tibetan Plateau from 2001 to 2012

2017 ◽  
Vol 37 (14) ◽  
pp. 4757-4767 ◽  
Author(s):  
Cunbo Han ◽  
Yaoming Ma ◽  
Xuelong Chen ◽  
Zhongbo Su
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Surface Heat ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Surface Heat Fluxes ◽  
Land Surface Heat Fluxes

On the Hyperbolicity of the Bulk Air–Sea Heat Flux Functions: Insights into the Efficiency of Air–Sea Moisture Disequilibrium for Tropical Cyclone Intensification

2021 ◽  
Vol 149 (5) ◽  
pp. 1517-1534
Author(s):  
Benjamin Jaimes de la Cruz ◽  
Lynn K. Shay ◽  
Joshua B. Wadler ◽  
Johna E. Rudzin
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Heat Content ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ocean Heat Uptake ◽  
Surface Heat Fluxes ◽  
Heat Uptake ◽  
Moisture Fluxes ◽  
New Perspective

AbstractSea-to-air heat fluxes are the energy source for tropical cyclone (TC) development and maintenance. In the bulk aerodynamic formulas, these fluxes are a function of surface wind speed U10 and air–sea temperature and moisture disequilibrium (ΔT and Δq, respectively). Although many studies have explained TC intensification through the mutual dependence between increasing U10 and increasing sea-to-air heat fluxes, recent studies have found that TC intensification can occur through deep convective vortex structures that obtain their local buoyancy from sea-to-air moisture fluxes, even under conditions of relatively low wind. Herein, a new perspective on the bulk aerodynamic formulas is introduced to evaluate the relative contribution of wind-driven (U10) and thermodynamically driven (ΔT and Δq) ocean heat uptake. Previously unnoticed salient properties of these formulas, reported here, are as follows: 1) these functions are hyperbolic and 2) increasing Δq is an efficient mechanism for enhancing the fluxes. This new perspective was used to investigate surface heat fluxes in six TCs during phases of steady-state intensity (SS), slow intensification (SI), and rapid intensification (RI). A capping of wind-driven heat uptake was found during periods of SS, SI, and RI. Compensation by larger values of Δq > 5 g kg−1 at moderate values of U10 led to intense inner-core moisture fluxes of greater than 600 W m−2 during RI. Peak values in Δq preferentially occurred over oceanic regimes with higher sea surface temperature (SST) and upper-ocean heat content. Thus, increasing SST and Δq is a very effective way to increase surface heat fluxes—this can easily be achieved as a TC moves over deeper warm oceanic regimes.

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