Research

Outline of My Research

MSE Budget Analysis of Strong and Weak MJO Events Using ERA5 and COSMIC RO Data: A Case-to-Case Comparison Study (M.S. Thesis)

To distinguish MJO propagation characteristics with recharge-discharge processes, I analyzed several strong/weak MJO events through gross moist stability plane.

Normailized gross moist stability (GMS) (Raymond 2007) and critical GMS (Inoue and Back 2015a, b):

Next, I focused on the development of a novel index called the “Recharge-Discharge Power” (RDP). Our findings revealed that MJO events with higher RDP indices exhibited greater intensity and propagation potential compared to those with lower indices.

Notably, RDP corresponds to the area enclosed by an ellipse over the MJO’s entire life cycle. To simplify the algorithm, I divided this ellipse into multiple triangular areas using Heron’s formula.

Recently, real time Multivariate MJO (RMM) index is a well-known tool for identifying the MJO’s position and phase, but the datasets it used are not totally from observation. Therefore, we selected the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation as our basis of monitoring system. Due to high resolution of layers and near-real time output in COSMIC-2, we expect that COSMIC-2 can offer instant temperature and moisture conditions for a new GMS plane using the gross moist stratification (Mq ) and gross dry stability (Mq).

Gross moist stratification and gross dry stability (Neelin and Yu 1994):

Since original COSMIC-2 data is level-2, I gridded it through objective analysis (Barnes 1964) over horizontal layer. For the moisture field, the three main wetter regions (Africa, MC and South America) in COSMIC-2 present similar features as in reanalysis data. Even though the pattern derived from the satellite is smooth, most of the correlation coefficients are up to 0.9.

Reference:

Barnes, S. L., 1964: A technique for maximizing details in numerical weather map analysis. Journal of Applied Meteorology and Climatology, 3, 396- 409.

Inoue, K., and L. Back, 2015a: Column-integrated moist static energy budget analysis on various time scales during TOGA COARE. Journal of the Atmospheric Sciences, 72, 1856-1871. 84.

Inoue, K., and L. E. Back, 2015b: Gross moist stability assessment during TOGA COARE: Various interpretations of gross moist stability. Journal of the Atmospheric Sciences, 72, 4148-4166.

Neelin, J. D., and J.-Y. Yu, 1994: Modes of tropical variability under convective adjustment and the Madden–Julian oscillation. Part I: Analytical theory. Journal of Atmospheric Sciences, 51, 1876-1894.

Raymond, D. J., and Ž. Fuchs, 2007: Convectively coupled gravity and moisture modes in a simple atmospheric model. Tellus A: Dynamic Meteorology and Oceanography, 59, 627-640.

The Recent Regime Shift of the Winter Madden-Julian Oscillation

High variance ratio (intraseaonal to mean state) of both thermodynamics and dynamics fields shows regime shift, indicating MJO signals exhibit more active over Maritime Continent (MC) during Second Period (P2: 2012-2023) than First Period(P1: 2000-2011), This result is linked with increase of low-level moisture and convergence in mean state in MC domain. More details in preparation or personal communication.

vertically integrated moist static energy (MSE) budget:

Figures belows show the MSE budget with intraseasonal variability. The tendency of MSE in Indian Ocean domian decreases while increases over MC domian. The vertical advection export (Import) MSE over IO (MC) region, demonstrating the vertical profile tends to be top-heavy (bottom-heavy), a representation of stabilization (destabilization) (Back and Bretherton 2006, Inoue and Back 2015, Bui et al. 2016).

Reference:

Back, L., and C. Bretherton, 2006: Geographic variability in the export of moist static energy and vertical motion profiles in the tropical Pacific. Geophysical research letters, 33, L17810.

Bui, H. X., J.-Y. Yu, and C. Chou, 2016: Impacts of vertical structure of largescale vertical motion in tropical climate: Moist static energy framework. Journal of the Atmospheric Sciences, 73, 4427-4437.

Inoue, K., and L. E. Back, 2015: Gross moist stability assessment during TOGA COARE: Various interpretations of gross moist stability. Journal of the Atmospheric Sciences, 72, 4148-4166.

Interplay of Diurnal Cycle over the Maritime Continent and MJO Propagation in CMIP6

We did some diagnostic analyses to investigate the emergent feature bwtween diurnal cycle over MC and MJO. (see poster in Conference below)

Now we conduct physical sensitivity experiments with entrainment rate of cumulus parameterization utilizing TaiESM1 climate model, which has a legacy from CESM family, to investigate impacts of entrainment rates on the simulated diurnal cycle and MJO. More details in preparation or personal communication.

Upcoming project

Deep Learning Filtering for the Tropical Variability

The convectional filtering methods for tropical variability is mathematic solution (e.g. FFT, Bandpass filter). Non-linear part of signal may be exluded by these methods. Previous studies demonstrates that intraseasonal variability can be subtracted through Convolutional Neural Network (Stan and Mantripragada 2023). Our work is to extract tropical variability by reconstructing embedding features and compare the results with filtered pattern through convectionl methods. Our scientific questions is " What patterns are important but excluded?"

Reference:

Stan, C., and R. S. S. Mantripragada, 2023: A Deep Learning Filter for the Intraseasonal Variability of the Tropics. Artif. Intell. Earth Syst., 2, e220079, https://doi.org/10.1175/AIES-D-22-0079.1.

Conference

Shu-Hsuan Lin, Yi-Chi Wang, Wan-Ling Tseng, Li-Chiang Jiang: Interplay of Diurnal Cycle over the Maritime Continent and MJO Propagation in CMIP6. Climate Hotspots in Action (CHIA) Forum 2023, Academia, Sinica, Taipei, Taiwan

Shu-Hsuan Lin, Jia-Yuh Yu: MSE Budget Analysis of Strong and Weak MJO Events Using ERA5 and COSMIC RO Data: A Case-to-Case Comparison Study. 2022 Atmospheric Science Graduate Conference, Taiwan Geosciences Assembly, Taipei, Taiwan

Chia_Forum Poster_v2.pdf

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