function change_weather () {
    var pref_id = document.getElementById('pref').value;
    document.getElementById('weather').src = 'http://image.weather.livedoor.com/component/img/plugin/weather_image/' + pref_id + '.gif';

}

function weather_detail () {
    var pref_id = document.getElementById('pref').value;
    switch (pref_id) {
      case "40" : window.open("http://weather.livedoor.com/area/40/110.html" , "_blank");
                break;
      case "41" : window.open("http://weather.livedoor.com/area/41/122.html" , "_blank");
                break;
      case "42" : window.open("http://weather.livedoor.com/area/42/118.html" , "_blank");
                break;
      case "43" : window.open("http://weather.livedoor.com/area/43/124.html" , "_blank");
                break;
      case "44" : window.open("http://weather.livedoor.com/area/44/114.html" , "_blank");
                break;
      case "45" : window.open("http://weather.livedoor.com/area/45/128.html" , "_blank");
                break;
      case "46" : window.open("http://weather.livedoor.com/area/46/132.html" , "_blank");
                break;
      case "47" : window.open("http://weather.livedoor.com/area/47/136.html" , "_blank");
                break;
    }
}