Coverage for src / CSET / operators / pressure.py: 100%

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, KAPPA, P0 

22from CSET.operators.misc import convert_units 

23 

24 

25def vapour_pressure( 

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

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

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

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

30 for T in iter_maybe(temperature): 

31 es = T.copy() 

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

33 es.data = E0 * np.exp(exponent.core_data()) 

34 es.units = "hPa" 

35 es.rename("vapour_pressure") 

36 v_pressure.append(es) 

37 if len(v_pressure) == 1: 

38 return v_pressure[0] 

39 else: 

40 return v_pressure 

41 

42 

43def vapour_pressure_from_relative_humidity( 

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

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

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

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

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

49 for T, RH in zip( 

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

51 ): 

52 RH = convert_units(RH, "1") 

53 vp = vapour_pressure(T) * RH 

54 vp.units = "hPa" 

55 vp.rename("vapour_pressure") 

56 v_pressure.append(vp) 

57 if len(v_pressure) == 1: 

58 return v_pressure[0] 

59 else: 

60 return v_pressure 

61 

62 

63def exner_pressure( 

64 pressure: iris.cube.Cube | iris.cube.CubeList, 

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

66 """Calculate the exner pressure.""" 

67 pi = iris.cube.CubeList([]) 

68 for P in iter_maybe(pressure): 

69 PI = P.copy() 

70 P = convert_units(P, "hPa") 

71 PI.data = (P.core_data() / P0) ** KAPPA 

72 PI.rename("exner_pressure") 

73 PI.units = "1" 

74 pi.append(PI) 

75 if len(pi) == 1: 

76 return pi[0] 

77 else: 

78 return pi