Adjust inter and extrapolation of gmt onto observation times

[swillner]

Before, the gmt time series was stretched to observation times and interpolated in between. This fixes the stretch by extrapolating the additional days missing at the end using xarray (https://docs.xarray.dev/en/stable/generated/xarray.DataArray.interp.html). So far, these have only been less than 10.

This change yields some minor differences in output values as below. This would be an opportunity to update the reference ("desired") data set using the new code.

• tas
  Mismatched elements: 40405 / 44925 (89.9%)
  Max absolute difference: 0.00268306
  Max relative difference: 9.56928877e-06
actual: array([265.938872, 263.537327, 263.393717, ..., 279.529727, 278.219363, 277.543571])
desired: array([265.938842, 263.537296, 263.393686, ..., 279.528476, 278.218048, 277.542196])

• tasskew
  Mismatched elements: 44201 / 44925 (98.4%)
  Max absolute difference: 0.00010132
  Max relative difference: 0.00030966
actual: array([0.59104 , 0.578195, 0.424484, ..., 0.455711, 0.426205, 0.509888])
desired: array([0.591039, 0.578194, 0.424483, ..., 0.455625, 0.42612 , 0.509804])

• tasrange
  Mismatched elements: 25232 / 44925 (56.2%)
  Max absolute difference: 0.00030414
  Max relative difference: 3.10712416e-05
actual: array([6.405501, 2.079143, 4.204534, ..., 1.656265, 2.627698, 2.978045])
desired: array([6.405501, 2.079143, 4.204533, ..., 1.656214, 2.627617, 2.977952])

• ps
  Mismatched elements: 36450 / 44925 (81.1%)
  Max absolute difference: 0.39365146
  Max relative difference: 4.08984222e-06
actual: array([98008.40417 , 98347.605052, 98528.59211 , ..., 97054.805638, 97274.423121, 96459.794494])
desired: array([98008.398762, 98347.599598, 98528.586623, ..., 97054.509612, 97274.114309, 96459.473709])

• hurs
  Mismatched elements: 37940 / 44925 (84.5%)
  Max absolute difference: 0.00069123
  Max relative difference: 1.37780455e-05
actual: array([92.909477, 91.312848, 87.183917, ..., 80.658298, 81.257607, 81.613646])
desired: array([92.909479, 91.312848, 87.183913, ..., 80.658329, 81.257634, 81.613666])

• rsds
  Mismatched elements: 44271 / 44925 (98.5%)
  Max absolute difference: 0.03822743
  Max relative difference: 0.0066553
actual: array([31.412014, 41.785989, 34.165635, ..., 10.850706, 27.515022, 20.244547])
desired: array([31.412037, 41.786009, 34.165653, ..., 10.852434, 27.5166 , 20.245965])

• rlsds
  Mismatched elements: 43121 / 44925 (96%)
  Max absolute difference: 0.01451909
  Max relative difference: 5.58586557e-05
actual: array([240.147832, 218.330501, 214.586922, ..., 326.129449, 285.942123, 285.195691])
desired: array([240.147845, 218.330517, 214.58694 , ..., 326.134107, 285.94692 , 285.200637])

• sfc_wind
  Mismatched elements: 40937 / 44925 (91.1%)
  Max absolute difference: 0.00020181
  Max relative difference: 2.92470805e-05
actual: array([3.44585 , 2.942172, 2.210839, ..., 6.969687, 4.79171 , 5.301441])
desired: array([3.44585 , 2.942172, 2.210839, ..., 6.96973 , 4.79174 , 5.301475])