Coverage for src / CSET / operators / pressure.py: 0%

1# © Crown copyright, Met Office (2022-2026) and CSET contributors. 

2# 

3# Licensed under the Apache License, Version 2.0 (the "License"); 

4# you may not use this file except in compliance with the License. 

5# You may obtain a copy of the License at 

6# 

7# http://www.apache.org/licenses/LICENSE-2.0 

8# 

9# Unless required by applicable law or agreed to in writing, software 

10# distributed under the License is distributed on an "AS IS" BASIS, 

11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 

12# See the License for the specific language governing permissions and 

13# limitations under the License. 

14 

15"""Operators for pressure conversions.""" 

16 

17import iris.cube 

18import numpy as np 

19 

20from CSET._common import iter_maybe 

21from CSET.operators.atmospheric_constants import E0 

22 

23 

24def vapour_pressure( 

25 temperature: iris.cube.Cube | iris.cube.CubeList, 

26) -> iris.cube.Cube | iris.cube.CubeList: 

27 """Calculate the vapour pressure of the atmosphere.""" 

28 v_pressure = iris.cube.CubeList([]) 

29 for T in iter_maybe(temperature): 

30 es = T.copy() 

31 exponent = 17.27 * (T - 273.16) / (T - 35.86) 

32 es.data[:] = E0 * np.exp(exponent.core_data()) 

33 es.units = "hPa" 

34 es.rename("vapour_pressure") 

35 v_pressure.append(es) 

36 if len(v_pressure) == 1: 

37 return v_pressure[0] 

38 else: 

39 return v_pressure 

40 

41 

42def vapour_pressure_from_RH( 

43 temperature: iris.cube.Cube | iris.cube.CubeList, 

44 relative_humidity: iris.cube.Cube | iris.cube.CubeList, 

45) -> iris.cube.Cube | iris.cube.CubeList: 

46 """Calculate the vapour pressure using RH.""" 

47 v_pressure = iris.cube.CubeList([]) 

48 for T, RH in zip( 

49 iter_maybe(temperature), iter_maybe(relative_humidity), strict=True 

50 ): 

51 if RH.units == "%": 

52 RH /= 100.0 

53 RH.units = "1" 

54 vp = vapour_pressure(T) * RH 

55 v_pressure.append(vp) 

56 if len(v_pressure) == 1: 

57 return v_pressure[0] 

58 else: 

59 return v_pressure