Turbulence flux condition in Jakarta during Cross Equatorial Northerly Surge (CENS)
Ahlil Ilmar Batuparan (1), I Dewa Gede A. Junnaedhi (1,2), M. Rais Abdillah (1,2), and Atsushi Inagaki (3)

a) Faculty of Earth Sciences and Technology, , Bandung Institute of Technology, Bandung, Indonesia

b) Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan

Abstract

Cross Equatorial Northerly Surge (CENS) causes the strengthening of monsoon winds from the north around the Karimata Strait and Java Sea. CENS was often associated with heavy rain in western Java, especially during the early morning. As a mesoscale process, CENS might influence microscale meteorological conditions such as turbulence fluxes. The micrometeorological observation campaign in two locations in Jakarta, namely KKP and LLH, gives the opportunity to study the effect of CENS on micrometeorological conditions. This study aims to examine how CENS change the micro-scale turbulence fluxes during wet season in Jakarta, Indonesia.
This study focused on wet seasons, between December and January, during the period of 2017 to 2022. The CENS period is defined using ERA5 surface wind data over 105 E to 115 E and 5 S. The turbulence fluxes were estimated using eddy covariance method (EC) from the micrometeorological observation data at KKP and LLH. The mean meteorological and turbulent fluxes condition then compared between CENS and non CENS period.
Although CENS causes stronger northerly winds, it does not have a significant influence on the turbulent momentum flux (Fm) in Jakarta. The turbulent sensible heat flux (QH) however, shows lower value during daytime, suggesting that CENS might suppress sensible heat transfer. The latent heat flux (QL) estimation at LLH also shows lower values during daytime under CENS occurrences. However, during early morning on CENS periods, the latent heat flux shows higher values. This result indicates that overland turbulence processes might induce early morning heavy rain that was observed during CENS period.

Keywords: CENS, Turbulent Flux, Jakarta, Micro-scale, Meso-scale

Topic: Atmospheric Sciences