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CHOCO-JEX: A Research Programme Focused on the CHOCO Low-level Jet
over the Far Eastern Pacific and Western Colombia - Reanalysis Evaluation
IntroductionThe Choco low-level jet (ChocoJet) is a
prominent circulation feature of the Intra-
Americas climate over the far eastern Pacific.
This jet contribute to wet seasons over the
Colombian Pacific coast and southern Central
America (Poveda & Mesa, 1999; 2000). The
structure and dynamics of the ChocoJet have
been studied using reanalysis products, but no
permanent upper-air soundings have been put
in place on the region neither for improving the
understanding of the ChocoJet nor for
evaluating the reanalysis skills in capturing its
dynamical and thermodynamical features. This
work shows a validation assessment of diverse
reanalysis using independent upper-air
soundings off-shore and inland the Colombian
Pacific during the 2016 Choco-JEX field
campaigns.
Results
References
Objective
• Bao, X., & F. Zhang (2012), Evaluation of NCEP/CFSR, NCEP/ NCAR, ERA-Interim, and ERA-40 reanalysis datasets
against independent sounding observations over the Tibetan Plateau. J. Climate, 26, 206–214.
• Poveda, G., & O. J. Mesa (1999), La corriente de chorro superficial del oeste (del Chocó) y otras dos corrientes de
chorro en Colombia: Climatología y variabilidad durante las fases del ENSO. Rev. Acad. Colomb. Cienc, 89: 517–528.
• Poveda, G., & O. J. Mesa (2000), On the existence of Lloró (the rainiest locality on Earth): Enhanced ocean-atmosphere-
land interaction by a low-level jet”. Geoph. Res. Lett., Vol. 27, No. 11, 1675-1678.
Acknowledgments:We thanks to personnel from Colombian Air Force, the Colombian Navy and Universidad Tecnológica
del Chocó (UTCH) involved in the IOPs. The work of J. Yepes was supported by COLCIENCIAS
Doctorate Fellowship Program. The work of G. Poveda has been supported by Universidad Nacional
de Colombia, and the work of J. F. Mejía was supported by Desert Research Institute.
Johanna Yepes1, John F. Mejía2 and Germán Poveda1
1 Department of Geosciences and Environment, Universidad Nacional de Colombia, Sede Medellín, Colombia2 Desert Research Institute, Reno, NV, United States
e-mail: [email protected]
To evaluate the skill of different reanalyses on
their ability to characterize the observed upper
atmosphere environment of the ChocoJet over
the far Eastern Pacific.
Mean vertical profiles and STD of T, q, U, V contrasting ChocoJEX observations
against CFSR, Era-Interim, MERRA and NCEP/NCAR reanalysis
FIGURE 1. (Left Panel) Vertical profiles of mean temperature (°C) (first column), specific humidity (g/kg) (second column), zonal (third column)
and meridional wind (m/s) (four column) averaged over each independent IOP1 (first row), IOP2 (second row), IOP3 (third row) and IOP4 (four
row) ChocoJEX soundings and CFSR, Era Interim, MERRA, NCEP-NCAR reanalysis (Right Panel) As in left panel but for the STD.
Bias and RMSE of T, q, U, V contrasting ChocoJEX observations
against CFSR, Era-Interim, MERRA and NCEP/NCAR reanalysis
FIGURE 2. (Left Panel) Vertical profiles of mean biases for each reanalysis compared against the independent IOP1 (first row), IOP2
(second row), IOP3 (third row) and IOP4 (four row) ChocoJEX soundings. Columns show results for temperature (°C) (first column), specific
humidity (g/kg) (second column), zonal wind (third column) and meridional wind (m/s) (four column) (Right Panel) As in left panel for RMSE.
Data and Methodology
CHOCO-JEX Experiment
Discussion
A pioneering interinstitutional partnership
among the National University of Colombia,
the Colombian Air Force, the Colombian
Navy and the Desert Research Institute
(University of NV) involving 4 week-long
Intensive Observing Periods (IOP) in 2016,
using 6-hourly upper-air soundings :
• IOP1: January 15-22 (Off-Shore).
• IOP2: Quibdó, June 25-Jul 1 (Inland).
• IOP3: Quibdó, October 15-22 (Inland).
• IOP4: November 21-28 (Off-Shore)
• Temperature (T), Specific Humidity, Zonal (U)
and Meridional Wind (V) using MW41 Vaisala
system and Radiosonde RS41-SG.
• Same upper-air parametros were retrieved
from CFSR (0.5°grid size), Era-Interim (0.75°),
MERRA(1.25°) and NCEP/NCAR (2.5°).
• Maritime observations were averaged over an
area defined by the vessel track.
• Validation metrics: Vertical Mean Profiles, Bias,
Standard Deviation (STD), and RSME (Bao
and Zhang, 2012).
T q U V T q U V
IOP1
(Off-Shore)
IOP2
(Inland)
IOP3
(Inland)
IOP4
(Off-Shore)
IOP1
(Off-Shore)
IOP2
(Inland)
IOP3
(Inland)
IOP4
(Off-Shore)
T q U V T q U V
• Despite the short duration of the 4 IOPs, all reanalysis show acceptable mean vertical profiles for T, q, U and V.
Maritime mean wind profiles are in better agreement than those over land.
• During IOP4, CFSR, Era-Interim and MERRA show deeper and stronger low-level ChocoJet structure (+1 m/s),
whereas the coarse NCEP/NCAR reanalysis does not capture ChocoJet.
• During IOP1, all reanalysis underestimate the Standard Deviation of all variables. They all failed to capture the
relatively higher mid-level variability exhibited by T (0.6°C) and q (1g/kg).
• CFSR and MERRA show warm systematic bias at 700 hPa (IOP1=1.5 °C, IOP2=0.5 °C, IOP= 0.5°C, IOP4=0.5 °C).
Also, they show wetter (drier) troposphere at mid (superficial) levels in the oceanic IOPs.
• CFSR, Era-Interim and NCEP/NCAR underestimate easterlies in mid-levels (<2 m/s) and overestimate easterlies at
lower levels (<4 m/s) in IOP1. In contrast, same reanalysis overestimate both easterlies in mid-levels (<2 m/s) and
westerlies at superficial levels (<2 m/s) in IOP4.
• Large RMSE are linked to strong changes in synoptic conditions (not shown).