def METHOD_NAME(diags: xr.Dataset) -> xr.DataArray:
    if (
        MASS_STREAMFUNCTION_MID_TROPOSPHERE not in diags
        or "water_vapor_path_zonal_mean_value" not in diags
    ):
        return xr.DataArray()
    psi = diags[MASS_STREAMFUNCTION_MID_TROPOSPHERE]
    wvp = diags["water_vapor_path_zonal_mean_value"]
    lat_min, lat_max = itcz_edges(psi)
    weights = np.cos(np.deg2rad(psi.latitude))
    weights = weights.where(psi.latitude > lat_min).where(psi.latitude < lat_max)
    ascent_region_mean = vcm.weighted_average(wvp, weights, ["latitude"])
    return ascent_region_mean.assign_attrs(
        long_name="Water vapor path in tropical ascent region"
    )