# Tropical Surface Temperature and Atmospheric Latent Heating: A Whole-Tropics Perspective Based on TRMM and ERA5 Datasets

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## Abstract

**:**

## 1. Introduction

## 2. Data and Methods

#### 2.1. Data

#### 2.2. Methods

## 3. Results

#### Climatology of Annual TLH, TST, Their Symmetric and Antisymmetric Parts

## 4. Summary and Discussion

- (1)
- (2)
- For the principal mode of TLH (and tropical rainfall) interannual variability, we find that equatorial symmetric components dominate only over a zonal band over from the near-Equator Indian Ocean to western and middle equatorial Pacific, salient equatorially antisymmetric variability exists over the middle and Eastern Pacific (Figure 5). In general, the symmetric and antisymmetric TLH exhibits high co-variability over most areas of the tropics (Figure 6b).
- (3)
- We find surprisingly that the spatial patterns of TLH projected upon the first principal components (PC1) of symmetric and antisymmetric TSTs over the whole-tropics, are very similar to each other, seemingly at odds with the classic Mastuno–Gill theory. The similarity in the projected TLH patterns is mainly due to the fact that the symmetric and antisymmetric PCs of TST are both nearly coincident with the ENSO index during the 21 years of 1998–2018.

## 5. Historical Note

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 2.**The left panel: (

**a**) climatology of the annual-mean TRMM-based tropical latent heating (TLH), and its (

**b**) symmetric and (

**c**) antisymmetric parts. Unit: $\mathrm{W}/{\mathrm{m}}^{2}$. The right panel: (

**d**) climatology of the annual-mean tropical surface temperature (TST) and its (

**e**) symmetric and (

**f**) antisymmetric parts. Units: °C.

**Figure 3.**The left (

**a**) and right (

**b**) spatial pattern of the first mode of SVD using TST and TRMM-based TLH. The squared covariance fraction of the first mode, expressed as a percent, is printed on the upper right-hand corner of each map. (

**c**,

**d**) and (

**e**,

**f**): same as (

**a**,

**b**), but using symmetric and antisymmetric components of TST and TLH, respectively. (

**g**,

**h**): The time series of the expansion coefficient of the three left patterns and three right patterns, respectively, the blue dotted line is the seasonal-averaged Nino 3.4 index.

**Figure 4.**The first EOF (EOF1) mode of the seasonal-mean: (

**a**) original, (

**b**) the symmetric part and (

**c**) antisymmetric components of TST over the whole-tropics, and (

**d**) the corresponding principle components for (

**a**–

**c**).

**Figure 5.**(

**a**) The correlation and (

**b**) the regression of the TRMM-based TLH with/onto the PC1 of equatorially symmetric TST. (

**c**) and (

**d**) are the symmetric and antisymmetric parts of (

**b**), respectively. (

**e**–

**h**) are the same as (

**a**–

**d**), but associated with the PC1 of equatorially antisymmetric TST. The areas with a significance level of less than 0.05 are dotted.

**Figure 6.**The local correlation between equatorially symmetric and antisymmetric components of (

**a**) TST and (

**b**) TRMM-based TLH. The areas with a significance level of less than 0.05 are dotted.

**Table 1.**The correlation coefficients between the time series of the expansion coefficient of three left and right SVD patterns.

r | Significance Level | |
---|---|---|

TST vs. TLH (original) | 0.9 | <0.01 |

Symmetric TST (TST_SYM) vs. original TLH | 0.89 | <0.01 |

Antisymmetric TST (TST_ASYM) vs. original TLH | 0.82 | <0.01 |

**Table 2.**The correlation coefficients between the time series of the expansion coefficient of three left and right SVD patterns and the Oceanic Niño Index.

r | Significance Level | |
---|---|---|

TST vs. ONI | 0.915 | <0.01 |

TLH (TST) vs. ONI | 0.933 | <0.01 |

TST_SYM vs. ONI | 0.928 | <0.01 |

TLH (TST_SYM) vs. ONI | 0.935 | <0.01 |

TST_ASYM vs. ONI | 0.763 | <0.01 |

TLH (TST_ASYM) vs. ONI | 0.925 | <0.01 |

**Table 3.**The correlation coefficients between the principle components of the EOF1 of TST, TST_SYM, and TST_ASYM.

r | Significance Level | |
---|---|---|

TST_PC1& TST_SYM_PC1 | 0.99 | <0.01 |

TST_PC1&TST_ASYM_PC1 | 0.87 | <0.01 |

TST_SYM_PC1&TST_ASYM_PC1 | 0.82 | <0.01 |

**Table 4.**The correlation coefficients between principle components of the EOF1 of TST, TST_SYM, TST_ASYM, and the Oceanic Niño Index.

R | Significance Level | |
---|---|---|

TST_PC1& ONI | 0.897 | <0.01 |

TST_SYM_PC1&ONI | 0.907 | <0.01 |

TST_ASYM_PC1&ONI | 0.721 | <0.01 |

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**MDPI and ACS Style**

Gao, Y.; Liu, X.; Lu, J.
Tropical Surface Temperature and Atmospheric Latent Heating: A Whole-Tropics Perspective Based on TRMM and ERA5 Datasets. *Remote Sens.* **2023**, *15*, 2746.
https://doi.org/10.3390/rs15112746

**AMA Style**

Gao Y, Liu X, Lu J.
Tropical Surface Temperature and Atmospheric Latent Heating: A Whole-Tropics Perspective Based on TRMM and ERA5 Datasets. *Remote Sensing*. 2023; 15(11):2746.
https://doi.org/10.3390/rs15112746

**Chicago/Turabian Style**

Gao, Yue, Xiaolin Liu, and Jianhua Lu.
2023. "Tropical Surface Temperature and Atmospheric Latent Heating: A Whole-Tropics Perspective Based on TRMM and ERA5 Datasets" *Remote Sensing* 15, no. 11: 2746.
https://doi.org/10.3390/rs15112746