North Temperate Lakes LTER: Ice Duration - Madison Lakes Area 1853 - current

Data include dates of freeze-up and thaw and ice duration of three primary lakes in the Madison area (Lake Mendota, Lake Monona, and Lake Wingra). Data are obtained from the State Climatologist. For Monona and Wingra, the freeze date (ice on) is defined as the first date on which the water body is observed to be completely ice covered, and the breakup date (ice off) is the date of the last breakup observed before the open water phase. Ice duration is the number of days that a water body is completely covered with ice and excludes any period during which the lake thawed in mid-winter before freezing again. For Mendota, duration is calculated in the same manner, but ice on and ice off dates are assigned as follows: The lake is deemed frozen if it has solid ice from Picnic Point to Maple Bluff and total ice cover is greater than 50 %. The lake is deemed open if it is ice-free from Picnic Point to Maple Bluff and total ice cover is less than 50%. Sampling Frequency: annually Number of sites: 3本数据集涵盖麦迪逊地区三座主要湖泊——门多塔湖（Lake Mendota）、莫诺纳湖（Lake Monona）与温格拉湖（Lake Wingra）——的封冻日期、解冻日期及冰期时长数据。数据源自州气候学家（State Climatologist）。针对莫诺纳湖与温格拉湖，封冻日期（ice on）指观测到水体完全被冰盖覆盖的首个日期，解冻日期（ice off）指开放水域阶段前观测到的最后一次冰盖破裂日期。冰期时长指水体完全被冰盖覆盖的累计天数，需排除冬季中期解冻后再次封冻的时段。就门多塔湖而言，冰期时长的计算方式与上述一致，但封冻与解冻日期的判定标准如下：若从野餐角（Picnic Point）至枫树崖（Maple Bluff）区域存在坚冰，且总冰盖覆盖率超过50%，则判定该湖泊处于封冻状态；若该区域无冰，且总冰盖覆盖率低于50%，则判定该湖泊处于无冰开放状态。采样频率：每年一次。监测站点数量：3个