You have to consider that:

- 1 kg of rain water spread over 1 square meter of surface is 1 mm in thickness;

- there are 60X60X24=86400 seconds in one day.

Therefore, 1 kg/m2/s = 86400 mm/day.

Considering that this would be an enormous amount of rain in a day by any standard, perhaps 1 kg/m2/s could be in reality 1 kg/m2/year, or per month, or per day. 1 kg/m2 is always 1 mm of rain.

Dear Elias,

You have to divide ERA-I by the density of water so you get m/s and then it's easy to convert into mm/day!

G.C.

You have to consider that:

- 1 kg of rain water spread over 1 square meter of surface is 1 mm in thickness;

- there are 60X60X24=86400 seconds in one day.

Therefore, 1 kg/m2/s = 86400 mm/day.

Considering that this would be an enormous amount of rain in a day by any standard, perhaps 1 kg/m2/s could be in reality 1 kg/m2/year, or per month, or per day. 1 kg/m2 is always 1 mm of rain.

If you are using Netcdf data, there CDO which can be used

cdo   mulc,86400     input.nc    ouput.nc 

From what i later found in the literature, ERA Interim total precipitation is given in metre(s)/day or m/d so i just had to multiply the values i had with 1000 to convert them to mm/day.

thank you all for your answers

Easiest way is to multiply by 86400 following the logic listed above by Roberto.

1 kg/m^2/sec = 1000 gm / (100cm)^2 /sec

= 1000 cm^3/(10000cm^2)/sec (1 cubic cm volume of water is 1 gm of water)

=1 cm/10/sec

=10 mm/10/sec

=1 mm/sec (86400 sec= 1 day, i.e. 1 sec= 1/86400 day)

= 1 mm /(1/86400)day

=86400 mm/day

Hi Elias,

If you have M/L^2/T and you whant L/T, just divide your Kg*m^-2/s by the density of the the water (check the water temperature), and then you have m^2/s what is the same of mm/s. Then you can change mm/s to mm/day.

First, convert days to second using;

60*60*24=86400sec

this is important because 1k.g. of a water spread over 1m^2 of surface 1mm in a thickness.

then if you're linux user, on terminal use the following approach (actually if you do have .nc file)

cdo mulc,86400 ifile ofile

but if you do have different variables first try to select the variable you want to convert using a command

cdo select,name=precip ifile ofile

you can use cdo or matlab for that .

cdo mulc,86400 data.nc out.nc

Use a unit analysis

mm/d=(precip kg/(m^2.s))*(1/ρ_water *m^3/kg)*(86400*s/d)*(1000 mm/m)

precip =precipitation

ρ_water= density of water or rain in kg/m3.

86400: number of seconds in a day

• 1 mm = 1 liter/ m2
• 1 liter = 1 kg
• 1 hr = 3600 s
• 3600 s x 24 hr (1 day) = 86400 s

To convert the precipitation of [kg/(m2 . s)] into (mm/day); we need to multiply 86400.

cdo mulc,86400 input.nc output.nc

You can use CDO by below command line

cdo mulc,86400 input.nc out.nc