Three Reanalysis Data Comparison and Monsoon Regional Analysis of Apparent Heat Source and Moisture Sink

겉보기 열원 및 습기 흡원의 세 재분석 자료 비교와 몬순 지역별 분석

Abstract

The roles of atmospheric heating formation and distribution on the global circulation are of utmost importance, and those are directly related to not only spatial but also temporal characteristics of monsoon system. In this study, before we clarify the characteristics of apparent heat source <$Q_1$> and moisture sink <$Q_2$>, comparisons of three reanalysis datasets (NCEP2, ERA-Interim, and JRA-55) in its global or regional patterns are performed to clearly evaluate differences among datasets. Considering inter-hemispheric difference of global monsoon regions, seasonal means of June-July-August and December-January-February, which is summer (winter) and winter (summer) in the Northern (Southern) Hemisphere are employed respectively. Here we show the characteristics of eight different regional monsoon regions and find contributions of <$Q_2$> to <$Q_1$> for the regional monsoon regions. Each term in apparent heat source and moisture sink is shown to come from the ERA-Interim dataset, since the ERA-Interim could be representative of three datasets. The NCEP2 data has a different characteristic in the ratio of <$Q_2$> and <$Q_1$> because it overestimates <$Q_1$> compared to the other two different datasets. The Australia monsoon has been performing better over time, while some regional monsoons (South America, North America, and North Africa) have been showing increasing data inconsistency. In addition, the three reanalysis datasets are getting different marching with time, in particular since the early 2000s over South America, North America, and North Africa monsoon regions. The recent inconsistency among the three datasets that may be associated with the global warming hiatus remains unexplored.

Fig. 1. Climatology of apparent heat source 1> [W m⁻²] and moisture sink 2> [W m⁻²] during December-January-February (DJF) for NCEP2 (left panels), ERA-Interim (middle panels), and JRA-55 (right panels).

Fig. 2. Same as Fig. 1, but for during June-July-August (JJA).

Fig. 3. Components of (a) apparent heat source 1> [W m⁻²] during December-January-February (DJF). Apparent heat source is composed of (b) horizontal advection of temperature [W m⁻²], (c) vertical advection of temperature [W m⁻²], (d) vertically integrated radiative heating [W m⁻²], (e) condensation heat released via precipitation [W m⁻²], and (f) sensible heat flux per unit area at the surface [W m⁻²].

Fig. 4. Components of (a) apparent moisture sink 2> [W m⁻²] during December-January-February (DJF). Apparent moisture sink is composed of (b) horizontal advection of moisture [W m⁻²], (c) vertical advection of moisture [W m⁻²], (d) condensation latent heat flux release via precipitation [W m⁻²], and (e) latent heat flux absorption via evaporation [W m⁻²].

Fig. 5. Same as Fig. 3, but for during June-July-August (JJA).

Fig. 6. Same as Fig. 4, but for during June-July-August (JJA).

Fig. 7. The area averaged (a) apparent heat source 1> [W m⁻²] and (b) moisture sink 2> [W m⁻²], and their ratio (2>/1>) in each regional monsoon region.

Fig. 8. Time series of apparent moisture sink 2> deviation among three datasets in (a) Australia, (b) South America, (c) North Africa, (d) North America summer monsoon regions.

Table 1. Datasets used in this study