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The land-sea thermal contrast is an important driver for monsoon interannual and interdecadal variability and the monsoon onset. The importance of the thermal contrast between the Tibetan Plateau (TP) and the Indian Ocean (IO) in driving the establishment of Indian Summer Monsoon (ISM) has been recognized. The South Asian Summer Monsoon (SASM) is primarily a tropical summer monsoon. As a direct dynamic response to the diabatic heating, the difference between upper and lower-layer winds can be closely linked to the strength of the heat source. The upper-layer thermal contrast is more important for the SASM (Sun et al., 2010; Sun and Ding，2011; Dai et al., 2013). Thermal contrast between the TP and the IO at the mid-upper troposphere is closely related to the onset and the variability of ISM. Considering that the temperature above the TP and IO are the two centers which are most sensitive to the change of ISM, a thermal contrast index (TCI) is proposed based on 500-200hPa air temperature:

TCI = Nor[T(25°N-38°N, 65°E-95°E) - T(5°S-8°N, 65°E-95°E)]

Where Nor represents standardization and T is 500-200hPa air temperature. The TCI is larger, and the ISM is stronger.

The TCI can capture the interannual and interdecadal variability of ISM well. The cooperative thermal effect between TP and IO may contributes more to the ISM than the separately temperature of TP or IO. In addition, from the view of climate mean state, the pentad-by-pentad increment of TCI has a 15-pentad lead when the correlation coefficient between it and the ISM index reaches the maximum. And the correlation coefficient between the pentad-by-pentad increment of TCI and the ISM index is significant when the pentad-by-pentad increment of TCI has a 3-pentad lead. The result indicates the advantage of the TCI for prediction of the ISM. Meanwhile, the averaged pentad-by-pentad increment of TCI for the first 25 (TCI25) pentads may be a predictor of the early or late onset of the ISM. The ISM onset will be earlier when the TCI25 is larger.

File naming and required software

STD_TCI_JJA_ERA_Interim_1979_2018.txt：Standardized summer (JJA, June-July-August) thermal contrast index (TCI) between the Tibetan plateau and the Indian Ocean during 1979-2017, calculated based on the ERA-Interim reanalysis data. There are two columns in the table. The first column represents the time (year), and the second column is the standardized TCI.
STD_TCI_Monthly_ERA_Interim_1979_2018.txt：Standardized monthly averaged thermal contrast index (TCI) between the Tibetan plateau and the Indian Ocean during 1979-2017, calculated based on the ERA-Interim reanalysis data. There are 13 columns in the table. The first column represents the year, the 2th to the 13th column are the standardized TCI from January to December respectively.
STD_TCI_Pentad_ERA_Interim_1979_2018.txt: Standardized pentad-by-pentad thermal contrast index (TCI) between the Tibetan plateau and the Indian Ocean during 1979-2017, calculated based on the ERA-Interim reanalysis data. There are 74 columns in the table. The first column represents the year, the 2th to the 73th column are the standardized TCI from the pentad 1 to the pentad 73 respectively.

Data Citations Data citation guideline What's data citation?

Li, Z., Xiao, Z., Zhao, L. (2019). Thermal contrast index (TCI) between the Tibetan Plateau and the Indian Ocean (1979-2018). A Big Earth Data Platform for Three Poles, DOI: 10.11888/Meteoro.tpdc.271017. CSTR: 18406.11.Meteoro.tpdc.271017. (Download the reference： RIS | Bibtex )

Using this data, the data citation is required to be referenced and the related literatures are suggested to be cited.

References literature

1.Sun, Y., Ding, Y., & Dai, A. (2010). Changing links between South Asian summer monsoon circulation and tropospheric land‐sea thermal contrasts under a warming scenario. Geophysical Research Letters, 37, L02704, doi:10.1029/2009GL041662. (View Details )

2.Dai, A., Li, H., Sun, Y., Hong, L., Linho, Chou, C., & Zhou, T. (2013). The relative roles of upper and lower tropospheric thermal contrasts and tropical influences in driving Asian summer monsoons. Journal of Geophysical Research, 118(13), 7024-7045. doi:10.1002/jgrd.50565. (View Details )

3.Yanai, M. H., Li, C. F., & Song, Z. S. (1992). Seasonal heating of the tibetan plateau and its effects on the evolution of the asian summer monsoon. Journal of the Meteorological Society of Japan, 70(1), 419-434. (View Details )

4.Ueda, H., & Yasunari, T. (1998). Role of warming over the Tibetan Plateau in early onset of the summer monsoon over the Bay of Bengal and the South China Sea. Journal of the Meteorological Society of Japan, 76(1), 1–12. (View Details )

5.Minoura, D., Kawamura, R., & Matsuura, T. (2003). A mechanism of the onset of the south Asian summer monsoon. Journal of the Meteorological Society of Japan, 81, 563–580. (View Details )

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Pan-Third Pole Environment Study for a Green Silk Road-A CAS Strategic Priority A Program (No:XDA20000000)

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