An evaluation of temperature and precipitation data for parks of the Mojave Desert Network

Jepson, Michael; Clabough, Tami; Caudill, Christopher; Qualls, Russel

We evaluated meteorological records from 23 sites in and near seven park units of the Mojave Desert Network (MOJN) to provide managers and planners with information on how climate is changing in their parks. We summarized monthly temperature and precipitation variables, including total precipitation during the monsoon season. We tested for monotonic trends in each time series using Mann-Kendall and Seasonal Mann-Kendall tests. Many locations had missing daily observations within months and we evaluated the rigor of test results to missing data by serially excluding mean monthly values from test iterations that had varying numbers of days missing from them. We used the metadata to determine when climate stations were relocated and we evaluated whether any observed temperature or precipitation trends may have been attributable to known station movements. Our findings were consistent with observations of regional warming and showed that most stations recorded warming during their periods of record. We found statistically significant warming trends in mean monthly temperature at 16 (~70%) of the 23 sites we evaluated. The proportion of sites with statistically significant (α < 0.05) warming trends in monthly mean minimum temperature (78%), monthly mean maximum temperature (61%), and minimum monthly temperature (74%) were similar. The evidence for significant warming in maximum monthly temperatures was less compelling, with only 8 (35%) of the 23 sites having positive trends. Only two sites associated with Joshua Tree NP and one site at Great Basin NP showed trends (increasing) in monsoonal precipitation. Evidence of trends in monthly precipitation data was also scant. Based on our changepoint analyses, station relocations appeared to have little effect on temperature results. In contrast, we found statistical evidence that some station relocations may have contributed to our failing to find any significant precipitation trends for those stations. Our sensitivity analysis suggested that the reported trends were insensitive to the number of days used to generate monthly climate values.

An evaluation of temperature and precipitation data for parks of the Mojave Desert Network

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