feat: ERA5 patcher + dummy pressure generator

Author: uniKorqi422

docs/notebooks/era5_to_rocketpy_patch.py

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+# era5_to_rocketpy_patch.py
+# Author: Amanda Wech
+# Mission: Make ERA5 NetCDF work with RocketPy EnvironmentAnalysis
+# Status: LIFTOFF ACHIEVED
+
+import xarray as xr
+import numpy as np
+import os
+
+def create_era5_compatible_surface(input_path, output_path, target_lat, target_lon):
+    """Patch ERA5 surface data to be RocketPy-compatible."""
+    print(f"Loading ERA5 surface: {input_path}")
+    ds = xr.open_dataset(input_path)
+
+    # Rename time
+    if 'valid_time' in ds:
+        ds = ds.rename({'valid_time': 'time'})
+        print("   → Renamed 'valid_time' to 'time'")
+
+    # Add v10, u100, v100
+    if 'v10' not in ds:
+        ds['v10'] = xr.zeros_like(ds['u10'])
+        print("   → Added 'v10' (zeroed)")
+    ds['u100'] = ds['u10']
+    ds['v100'] = ds['v10']
+    print("   → Added u100/v100")
+
+    # Required variables
+    for var, val in {'t2m': 293.15, 'sp': 95000.0, 'tp': 0.0, 'z': 0.0}.items():
+        if var not in ds:
+            ds[var] = ds['u10'] * 0 + val
+            print(f"   → Added '{var}' = {val}")
+
+    # Optional variables
+    for var, val in {'cbh': 1000.0, 'i10fg': 10.0, 'tcc': 0.0, 'blh': 500.0,
+                     'sshf': 0.0, 'slhf': 0.0, 'ssrd': 0.0}.items():
+        if var not in ds:
+            ds[var] = ds['u10'] * 0 + val
+            print(f"   → Added '{var}' = {val}")
+
+    # Snap to grid
+    lats = ds['latitude'].values
+    lons = ds['longitude'].values
+    best_lat = float(lats[np.argmin(np.abs(lats - target_lat))])
+    best_lon = float(lons[np.argmin(np.abs(lons - target_lon))])
+    dist_km = ((target_lat - best_lat)**2 + (target_lon - best_lon)**2)**0.5 * 111
+    print(f"   → Grid point: ({best_lat}, {best_lon}) | ~{dist_km:.1f} km")
+
+    ds.to_netcdf(output_path)
+    print(f"ERA5 SURFACE PATCHED → {output_path}")
+    ds.close()
+    return best_lat, best_lon
+
+
+def create_dummy_pressure(output_path, best_lat, best_lon):
+    """Create 2x2 dummy pressure file to avoid RocketPy index bugs."""
+    if os.path.exists(output_path):
+        os.remove(output_path)
+        print(f"Deleted old: {output_path}")
+
+    lat_vals = np.array([best_lat - 0.1, best_lat + 0.1])
+    lon_vals = np.array([best_lon - 0.1, best_lon + 0.1])
+    level_vals = np.array([1000, 850, 700, 500, 300, 200, 100])
+    time_vals = np.array([], dtype='datetime64[h]')
+    shape = (0, len(level_vals), 2, 2)
+    empty_4d = np.full(shape, np.nan)
+
+    ds = xr.Dataset(
+        {
+            'u': (['time', 'level', 'latitude', 'longitude'], empty_4d),
+            'v': (['time', 'level', 'latitude', 'longitude'], empty_4d),
+            't': (['time', 'level', 'latitude', 'longitude'], empty_4d),
+            'z': (['time', 'level', 'latitude', 'longitude'], empty_4d),
+        },
+        coords={
+            'time': ('time', time_vals),
+            'level': ('level', level_vals, {'units': 'hPa'}),
+            'latitude': ('latitude', lat_vals, {'units': 'degrees_north'}),
+            'longitude': ('longitude', lon_vals, {'units': 'degrees_east'})
+        }
+    )
+    ds.to_netcdf(output_path)
+    print(f"DUMMY PRESSURE CREATED → {output_path}")