Initial import of NavSea pbf project

tasks/updatedownload.md

@@ -0,0 +1,264 @@
+# NavSea Weather Server
+Task: WeatherServer_GFS_Subset_Downloader
+Architecture: V11
+Codex: codex6
+Status: TODO
+
+---
+
+# 任务目标
+
+升级现有 gfs_downloader.py
+
+当前问题：
+
+直接下载完整 GFS 文件：
+
+gfs.t00z.pgrb2.0p25.f000
+
+文件大小：
+
+≈ 500MB
+
+下载 72 小时预测需要：
+
+≈ 12GB
+
+这是不可接受的。
+
+解决方案：
+
+使用 NOAA 提供的 GRIB Subset API：
+
+filter_gfs_0p25.pl
+
+只下载：
+
+1 指定区域
+2 指定变量
+3 指定高度层
+
+目标：
+
+将单个 GRIB 文件缩小到：
+
+2MB – 10MB
+
+---
+
+# 下载区域
+
+NavSea 天气服务器只需要日本附近区域：
+
+leftlon = 120
+rightlon = 150
+toplat = 50
+bottomlat = 20
+
+覆盖：
+
+日本海
+东海
+太平洋日本海域
+
+---
+
+# 下载变量
+
+Weather System V1 需要以下变量：
+
+UGRD
+VGRD
+APCP
+PRMSL
+TMP
+HTSGW
+DIRPW
+PERPW
+
+说明：
+
+UGRD VGRD → 风
+APCP → 降水
+PRMSL → 气压
+TMP → 温度
+HTSGW → 浪高
+DIRPW → 浪方向
+PERPW → 浪周期
+
+变量参数来自 NOAA GFS 参数列表。 :contentReference[oaicite:0]{index=0}
+
+---
+
+# 下载高度层
+
+需要以下层：
+
+10 m above ground
+surface
+mean sea level
+
+参数：
+
+lev_10_m_above_ground
+lev_surface
+lev_mean_sea_level
+
+---
+
+# URL 构造规则
+
+基础地址：
+
+https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p25.pl
+
+示例：
+
+https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p25.pl?
+file=gfs.t00z.pgrb2.0p25.f003
+&lev_10_m_above_ground=on
+&lev_surface=on
+&lev_mean_sea_level=on
+&var_UGRD=on
+&var_VGRD=on
+&var_APCP=on
+&var_PRMSL=on
+&var_TMP=on
+&var_HTSGW=on
+&var_DIRPW=on
+&var_PERPW=on
+&leftlon=120
+&rightlon=150
+&toplat=50
+&bottomlat=20
+&dir=%2Fgfs.20260312%2F00%2Fatmos
+
+---
+
+# 修改文件
+
+weather_server/downloader/gfs_downloader.py
+
+---
+
+# 新代码
+
+```python
+import os
+import requests
+from datetime import datetime
+
+BASE_URL = "https://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_0p25.pl"
+
+OUTPUT_DIR = "data/grib"
+
+FORECAST_HOURS = [
+0,3,6,9,12,15,18,21,24,
+27,30,33,36,39,42,45,
+48,51,54,57,60,63,66,
+69,72
+]
+
+REGION = {
+"leftlon":120,
+"rightlon":150,
+"toplat":50,
+"bottomlat":20
+}
+
+VARIABLES = [
+"UGRD",
+"VGRD",
+"APCP",
+"PRMSL",
+"TMP",
+"HTSGW",
+"DIRPW",
+"PERPW"
+]
+
+LEVELS = [
+"lev_10_m_above_ground",
+"lev_surface",
+"lev_mean_sea_level"
+]
+
+os.makedirs(OUTPUT_DIR, exist_ok=True)
+
+
+def get_cycle():
+
+    now = datetime.utcnow()
+
+    hour = (now.hour // 6) * 6
+
+    cycle = f"{hour:02d}"
+
+    date = now.strftime("%Y%m%d")
+
+    return date, cycle
+
+
+def build_url(date, cycle, fh):
+
+    filename = f"gfs.t{cycle}z.pgrb2.0p25.f{fh}"
+
+    params = {
+        "file": filename,
+        "leftlon": REGION["leftlon"],
+        "rightlon": REGION["rightlon"],
+        "toplat": REGION["toplat"],
+        "bottomlat": REGION["bottomlat"],
+        "dir": f"/gfs.{date}/{cycle}/atmos"
+    }
+
+    for v in VARIABLES:
+        params[f"var_{v}"] = "on"
+
+    for l in LEVELS:
+        params[l] = "on"
+
+    return BASE_URL, params
+
+
+def download_file(url, params, path):
+
+    if os.path.exists(path):
+        print("skip", path)
+        return
+
+    print("downloading", path)
+
+    r = requests.get(url, params=params, stream=True)
+
+    if r.status_code != 200:
+        print("failed", r.status_code)
+        return
+
+    with open(path, "wb") as f:
+        for chunk in r.iter_content(1024*1024):
+            f.write(chunk)
+
+
+def main():
+
+    date, cycle = get_cycle()
+
+    print("cycle:", date, cycle)
+
+    for fh in FORECAST_HOURS:
+
+        fh_str = f"{fh:03d}"
+
+        url, params = build_url(date, cycle, fh_str)
+
+        output = os.path.join(
+            OUTPUT_DIR,
+            f"{date}_{cycle}_f{fh_str}.grib2"
+        )
+
+        download_file(url, params, output)
+
+
+if __name__ == "__main__":
+    main()