Identification

Title

What controls the interannual variation of the wet season onsets over the Amazon?

Abstract

Previous studies have established that sea surface temperature anomalies (SSTAs) in the tropical Pacific and Atlantic are the main forcing of the interannual variation of the wet season onsets in the Amazon. However, this variation appears to be complex and not uniquely determined by SSTAs. What causes such a complexity and to what extent the interannual variation of the wet season onsets is predictable remain unclear. This study suggests that such a complex relationship is the result of several competing processes, which are nonlinearly related to the SSTAs. In particular, three dry season conditions are crucial for determining interannual variation of the wet season onset. (i) A poleward shift of the Southern Hemisphere subtropical jet (SHSJ) over the South American sector, initiated from a wave train-like structure possibly forced by south central Pacific SST patterns, can prevent cold frontal systems from moving northward into the Amazon. This delays cold air incursion and results in late wet season onset over the southern Amazon. (ii) An anomalous anticyclonic center, which enhances westerly wind at 850 hPa over the southern Amazon and also the South American low-level jets, leads to moisture export from the southern Amazon to La Plata basin and reduces convective systems that provide elevated diabatic heating. (iii) Smaller convective available potential energy (CAPE) limits local thermodynamically driven convection. Based on the stepwise and partial least squares regressions, these three selected preseasonal conditions (Niño 4, SHSJ, and CAPE) can explain 57% of the total variance of the wet season onset.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7sn09w6

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2014-03-16T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact