| import numpy as np |
|
|
|
|
| def rainrate_to_reflectivity(rainrate: np.ndarray) -> np.ndarray: |
| """ |
| Convert rain rate to reflectivity using the Marshall-Palmer relationship. |
| |
| Applies Z = 200 * R^1.6 and converts to dBZ. Values below ~0.037 mm/h |
| are clipped to 0 dBZ; values above 60 dBZ are clipped to 60. |
| |
| Parameters |
| ---------- |
| rainrate : np.ndarray |
| Rain rate in mm/h. Can be any shape. |
| |
| Returns |
| ------- |
| reflectivity : np.ndarray |
| Reflectivity in dBZ, clipped to [0, 60]. Same shape as input. |
| """ |
| epsilon = 1e-16 |
| |
| return (10 * np.log10(200 * rainrate**1.6 + epsilon)).clip(0, 60) |
|
|
|
|
| def normalize_reflectivity(reflectivity: np.ndarray) -> np.ndarray: |
| """ |
| Normalize reflectivity from [0, 60] dBZ to [-1, 1]. |
| |
| Parameters |
| ---------- |
| reflectivity : np.ndarray |
| Reflectivity in dBZ, expected in [0, 60]. Can be any shape. |
| |
| Returns |
| ------- |
| normalized : np.ndarray |
| Normalized reflectivity in [-1, 1]. Same shape as input. |
| """ |
| return (reflectivity / 30.0) - 1.0 |
|
|
|
|
| def denormalize_reflectivity(normalized: np.ndarray) -> np.ndarray: |
| """ |
| Denormalize from [-1, 1] back to [0, 60] dBZ reflectivity. |
| |
| Parameters |
| ---------- |
| normalized : np.ndarray |
| Normalized reflectivity in [-1, 1]. Can be any shape. |
| |
| Returns |
| ------- |
| reflectivity : np.ndarray |
| Reflectivity in dBZ, in [0, 60]. Same shape as input. |
| """ |
| return (normalized + 1.0) * 30.0 |
|
|
|
|
| def reflectivity_to_rainrate(reflectivity: np.ndarray) -> np.ndarray: |
| """ |
| Convert reflectivity back to rain rate using the inverse Marshall-Palmer |
| relationship. |
| |
| Applies R = (Z_linear / 200)^(1/1.6) where Z_linear = 10^(dBZ/10). |
| |
| Parameters |
| ---------- |
| reflectivity : np.ndarray |
| Reflectivity in dBZ. Can be any shape. |
| |
| Returns |
| ------- |
| rainrate : np.ndarray |
| Rain rate in mm/h. Same shape as input. |
| """ |
| |
| |
| z_linear = 10 ** (reflectivity / 10.0) |
| return (z_linear / 200.0) ** (1.0 / 1.6) |
|
|
|
|
| def rainrate_to_normalized(rainrate: np.ndarray) -> np.ndarray: |
| """ |
| Convert rain rate directly to normalized reflectivity. |
| |
| Composes :func:`rainrate_to_reflectivity` and |
| :func:`normalize_reflectivity`. |
| |
| Parameters |
| ---------- |
| rainrate : np.ndarray |
| Rain rate in mm/h. Can be any shape. |
| |
| Returns |
| ------- |
| normalized : np.ndarray |
| Normalized reflectivity in [-1, 1]. Same shape as input. |
| """ |
| reflectivity = rainrate_to_reflectivity(rainrate) |
| return normalize_reflectivity(reflectivity) |
|
|
|
|
| def normalized_to_rainrate(normalized: np.ndarray) -> np.ndarray: |
| """ |
| Convert normalized reflectivity back to rain rate. |
| |
| Composes :func:`denormalize_reflectivity` and |
| :func:`reflectivity_to_rainrate`. |
| |
| Parameters |
| ---------- |
| normalized : np.ndarray |
| Normalized reflectivity in [-1, 1]. Can be any shape. |
| |
| Returns |
| ------- |
| rainrate : np.ndarray |
| Rain rate in mm/h. Same shape as input. |
| """ |
| reflectivity = denormalize_reflectivity(normalized) |
| return reflectivity_to_rainrate(reflectivity) |
|
|
