Dear Kazeem

The honest answer is that you cannot dis-aggregate annual rainfall to a one minute rainfall rate, because the results will be so uncertain that they will be meaningless. Even dis-aggregating 24 hour rainfall to a one minute rainfall rate is often not advisable, unless a dis-aggregation function based on observed short duration rainfall close to the location where the 24 hour rainfall has been measured is available.

I presume that from your affiliation that you are based in Nigeria? If you are looking for information on rainfall intensity for Nigeria it might be best to look at work others have carried out for example:

https://pdfs.semanticscholar.org/a439/9b911c0cb4c187d87babaab5f433d6335e6c.pdf

Article Rainfall-Intensity-Duration-Frequency Models for Selected Ci...

Article Deriving rainfall intensity-duration-frequency relationships...

I've not had time to read these paper but they may be useful to you.

Best regards

Darren

You can follow these articles

1-Minute Integrated Rain Rate Statistics Estimated From Tropical Rainfall Measuring Mission Data ( https://www.researchgate.net/publication/239937554_1-Minute_Integrated_Rain_Rate_Statistics_Estimated_From_Tropical_Rainfall_Measuring_Mission_Data)

60-to 1-Min Rainfall-Rate Conversion: Comparison of Existing Prediction Methods with Data Obtained in the Southeast Asia Region (https://journals.ametsoc.org/doi/pdf/10.1175/2007JAMC1600.1)

Kazeem Salaudeen I am going to agree with Darren Lumbroso There are several likely problems. Let's use Nigeria as the example. First, rainfall varies significantly monthly, and the yearly average may not represent any particular day. If that is true, how can a yearly total be disaggregated to represent a minute? Second, In Nigeria, you can have up to 600 mm rainfall/month in some places, and zero in some months. So, even if you want to try and model this, somehow you have to have a way to replace the means with "0" for times when you know the rainfall is zero and not the mean. Third, you have a space problem; rainfall is not consistent across all locations in Nigeria. In the paper Sheikh Mohammad Famim Ahmed posted, they used monthly data.

Here is another example, which also has the regional measures added: https://www.longdom.org/open-access/statistical-modeling-of-monthly-rainfall-in-selected-stations-in-forest-and-savannah-ecoclimatic-regions-of-nigeria-2332-2594-1000226.pdf

Thank you all

Dear Kazeem Salaudeen ,

This will result in lot of uncertainties.

Thanks all, but does that mean monthly rain rate data also cannot be converted to 1-minute integration time

I posted a reference for your use which converts from monthly. While it has been done, the questions are what are you doing with the data? How accurate do you need the minute estimates to be to accomplish what you want? Is it a good idea to estimate a minute from a month? There are at least 43,200 minutes in a month....how much does each minute represent the total for the month? Does it rain as much during the day as the night? In the morning versus the afternoon? At the beginning of the month and the end of the month? This is a lot of variability.....

Thanks Michael J. Lynch Miyuru Bandara Gunathilake Darren Lumbroso Sheikh Mohammad Famim Ahmed .So the best way to convert to one minute integration time is to monthly data and not annual data

Dear Kazeem Salaudeen, if you only have monthly measurements of the rainfall rate, you can use the Rice-Holmberg model, as well as the Refined Moupfouma-Martin model together with TT (see paper Rainfall Rate and Rain Attenuation Contour Maps for Preliminary “Simon Bolivar” Satellite Links Planning in Venezuela), knowing that the results obtained will present errors in relation to the real behavior of the complementary cumulative distribution of rainfall rate with 1-minute integration time, of the location.

Dear Kazeem Salaudeen, if you only have monthly measurements of the rainfall rate, you can use the Rice-Holmberg model, as well as the Refined Moupfouma-Martin model together with Chebil-Rahman model (see paper Rainfall Rate and Rain Attenuation Contour Maps for Preliminary “Simon Bolivar” Satellite Links Planning in Venezuela), knowing that the results obtained will present errors in relation to the real behavior of the complementary cumulative distribution of rainfall rate with 1-minute integration time, of the location.