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# Copyright (c) 2008-2015 MetPy Developers. |
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# Distributed under the terms of the BSD 3-Clause License. |
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# SPDX-License-Identifier: BSD-3-Clause |
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"""Contains calculation of various derived indicies.""" |
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import numpy as np |
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from ..calc import mixing_ratio, saturation_vapor_pressure |
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from ..calc.tools import get_layer |
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from ..constants import g, rho_l |
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from ..package_tools import Exporter |
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from ..units import units |
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exporter = Exporter(globals()) |
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def precipitable_water(dewpt, p, top=400 * units('hPa')): |
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r"""Calculate precipitable water through the depth of a sounding. |
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Default layer depth is sfc-400 hPa. Formula used is from p. 170 in |
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An Introduction to Atmospheric Thermodynamics by Anastasios A. Tsonis |
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(2007): |
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\begin{align} |
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\frac{1}{pg} \int\limits_0^d x \,dp |
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\end{align} |
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Tsonis, A. A., 2008: An introduction to atmospheric thermodynamics. |
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Cambridge Univ. Press, Cambridge. |
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Parameters |
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---------- |
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dewpt : array-like |
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Atmospheric dewpoint profile |
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p : array-like |
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Atmospheric pressure profile |
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top: `pint.Quantity` |
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The top of the layer, specified in pressure. |
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Returns |
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------- |
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`pint.Quantity' |
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The precipitable water in the layer, in inches |
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""" |
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pw_layer, dewpt_layer = get_layer(p, dewpt, depth=p[0] - top) |
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w = mixing_ratio(saturation_vapor_pressure(dewpt_layer), pw_layer) |
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sort_inds = np.argsort(pw_layer) |
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pw_layer = pw_layer[sort_inds] |
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w = w[sort_inds] |
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pw = pw = np.trapz(w, pw_layer) / (g * rho_l) |
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pw = ((pw.magnitude * 100) * units('meter')).to('inches') |
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return pw |
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Unidata /
MetPy
