Title: On the controls of daytime precipitation in the Amazonian dry season

Abstract

The Amazon plays an important role in the global energy and hydrological budgets. The precipitation during the dry season (June September) plays a critical role in maintaining the extent of the rain forest. The deployment of the first Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF-1) in the context of the Green Ocean Amazon (GOAmazon) field campaign at Manacapuru, Brazil, provided comprehensive measurements of surface, cloud, precipitation, radiation, and thermodynamic properties for two complete dry seasons (2014 and 2015). The precipitation events occurring during the nighttime were associated with propagating storm systems (nonlocal effects), while the daytime precipitation events were primarily a result of local land-atmosphere interactions. During the two dry seasons, precipitation was recorded at the surface on 106 days (43%) from 158 rain events with 82 daytime precipitation events occurring on 64 days (60.37%). Detailed comparisons between the diurnal cycles of surface and profile properties between days with and without daytime precipitation suggested the increased moisture at low and midlevels to be responsible for lowering the lifting condensation level, reducing convective inhibition and entrainment, and thus triggering the transition from shallow to deep convection. Although the monthly accumulated rainfall decreased during the progression of the dry season, the contributionmore » of daytime precipitation to it increased, suggesting the decrease to be mainly due to reduction in propagating squall lines. The control of daytime precipitation during the dry season on large-scale moisture advection above the boundary layer and the total rainfall on propagating squall lines suggests that coarse-resolution models should be able to accurately simulate the dry season precipitation over the Amazon basin.« less

Authors:

Ghate, Virendra P. ^[1]; Kollias, Pavlos ^[2]

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+ Show Author Affiliations

1. Argonne National Lab. (ANL), Lemont, IL (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., State Univ. of New York, Stony Brook, NY (United States)

Publication Date:

Fri Dec 16 00:00:00 EST 2016

Research Org.:

Brookhaven National Laboratory (BNL), Upton, NY (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23), Atmospheric System Research; Atmospheric Radiation Measurement (ARM) Program

OSTI Identifier:

1347371

Alternate Identifier(s):

OSTI ID: 1362121

Report Number(s):

BNL-113652-2017-JA
Journal ID: ISSN 1525-755X; R&D Project: 2016-BNL-EE630EECA-Budg; KP1701000

Grant/Contract Number:  

SC00112704; AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Hydrometeorology

Additional Journal Information:

Journal Volume: 17; Journal Issue: 12; Journal ID: ISSN 1525-755X

Publisher:

American Meteorological Society

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Amazon region; clouds; convection; atmosphere-land interaction; humidity; amazon; clouds, amazon, precipitation; precipitation