I would suggest that this problem is analogous to merging of radar rainfall estimates and raingauge data, since the radar is represented by a grid of values (similar presumably to the satellite?) and the gauge observations are spot values at different x-y locations within the grid, not necessarily at the nodes.

Therefore I would suggest you look at kriging or co-kriging methods as a way of combining the two data fields and producing a calibrated joint estimate. Early papers tended to regard the gauge data as "ground truth" and arrange to correct the radar data, but more recently it has beome obvious that both sets of observations have (different) errors and that a way of combining so as to minimise the errors is needed.

The following papers may be of use in this regard...

Krajewski, W.F., 1987. Cokriging radar-rainfall and rain gage data. J. Geophys. Res. Atmospheres 1984–2012 92, 9571–9580.

Ochoa-Rodriguez, S., Wang, L.-P., Grist, A., Allitt, R., Onof, C., Maksimović, Č., 2013. Improving the applicability of radar rainfall estimates for urban pluvial flood modelling and forecasting, in: Urban Drainage Group Autumn Conference and Exhibition.

Sinclair, S., Pegram, G., 2005. Combining radar and rain gauge rainfall estimates using conditional merging. Atmospheric Sci. Lett. 6, 19–22.

Wang, L.-P., Ochoa-Rodríguez, S., Simões, N.E., Onof, C., Maksimović, Č., others, 2013. Radar-raingauge data combination techniques: a revision and analysis of their suitability for urban hydrology. Water Sci Technol 68, 737.

OK. Certainly. Statistical Evaluation of Combined Daily Gauge Observations and Rainfall Satellite Estimates over Continental South America DANIEL A. VILA Cooperative Institute of Climate Studies, and Earth System Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland LUIS GUSTAVO G. DE GONCALVES Hydrological Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, and Earth System Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland DAVID L. TOLL Hydrological Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland JOSE ROBERTO ROZANTE CPTEC/INPE, Cachoeira Paulista, Sa˜o Paulo, Brazil (Manuscript received 25 April 2008, in final form 5 September 2008)

I think exploring the GPM IMERGE documents will  certainly help. Here are some references from that group:

Huffman, G.J., R.F. Adler, D.T. Bolvin, G. Gu, E.J. Nelkin, K.P. Bowman, Y. Hong, E.F.

Stocker, D.B. Wolff, 2007a: The TRMM Multi-satellite Precipitation Analysis: Quasi-

Global, Multi-Year, Combined-Sensor Precipitation Estimates at Fine Scale. J.

Hydrometeor., 8(1), 38-55. PDF available at ftp://meso.gsfc.nasa.gov/agnes/huffman/papers/

TMPA_jhm_07.pdf.gz

Huffman, G.J., R.F. Adler, D.T. Bolvin, E.J. Nelkin, 2010: The TRMM Multi-satellite

Precipitation Analysis (TMPA). Chapter 1 in Satellite Rainfall Applications for Surface

Hydrology, F. Hossain and M. Gebremichael, Eds. Springer Verlag, ISBN: 978-90-481-

2914-0, 3-22.

Huffman, G.J., R.F. Adler, S. Curtis, D.T. Bolvin, E.J. Nelkin, 2007b: Global Rainfall Analyses

at Monthly and 3-hr Time Scales. Chapter 23 of Measuring Precipitation from Space:

EURAINSAT and the Future, V. Levizzani, P. Bauer, and F.J. Turk, Eds., Springer Verlag

(Kluwer Academic Pub. B.V.), Dordrecht, The Netherlands, 291-306. [Invited paper]

Huffman, G.J., D.T. Bolvin, 2015: Transition of 3B42/3B43 Research Product from Monthly to

Climatological Calibration/Adjustment. URL, 11 pp.

Huffman, G.J., D.T. Bolvin, D. Braithwaite, K. Hsu, R. Joyce, P. Xie, 2014: GPM Integrated

Multi-Satellite Retrievals for GPM (IMERG) Algorithm Theoretical Basis Document

(ATBD) Version 4.4. PPS, NASA/GSFC, 30 pp. http://pmm.nasa.gov/sites/default/files/

document_files/IMERG_ATBD_V4.4.pdf

Dear Kazunori,

The TMPA product (the TRMM 3B42 and not the TRMM 3B42RT) is gauge corrected using data from the GPCP global gauge analysis. Details of the calibration are written in this paper (http://journals.ametsoc.org/doi/full/10.1175/JHM560.1), but if you are looking for the exact gauges used you should look into the GPCP product.

Moreover, make sure you are using the TRMM 3B42 product which is the climatology product. If you use the TRMM 3B42 RT (real time product) it does not have gauge correction.

Good luck.

The TMPA research product (TRMM 3B42) already includes a gauge correction using a global dataset. However, this might exclude information from local networks of limited access.

Therefore, I would also suggest to have a look at satellite - rain gauge merging algorithms. Here you will find a recent paper on the subject, which also includes many helpful references.

Article A Comparative Analysis of TRMM-Rain Gauge Data Merging Techn...

I think the TMPA research product  includes the  gauge correction using a global dataset. It maybe better if you check the  satellite rainfall and  gauge  data merging algorithms. I would like to suggest you look through the paper( 

A comparative analysis of TRMM-rain gauge data merging techniques at the daily time scale for distributed rainfall-runoff modelling applications. Daniele Nerini et al. 2015; 16(5):2153-2168. DOI: 10.1175/JHM-D-14-0197.1

This would be greatly helpful.

as additional reference, maybe you can look this paper:

Schneider, U., Becker, A., Finger, P., Meyer-Christoffer, A., Ziese, M., & Rudolf, B. (2014). GPCC's new land surface precipitation climatology based on quality-controlled in situ data and its role in quantifying the global water cycle. Theoretical and Applied Climatology, 115(1-2), 15-40. (http://link.springer.com/article/10.1007/s00704-013-0860-x)

The gauge analysis used in the IMERG, TMPA, and GPCP datasets is produced by the Global Precipitation Climatology Centre (part of the Deutscher Wetterdienst).  Their long-standing practice of not releasing gauge data was instituted to coax data from institutions who think of their data as proprietary or a state secret.  However, for any given region they are willing to tell you which stations are typically used for a given period of time.  Andreas Becker is the GPCC head.