Long-Term Trend Analysis in Annual and Seasonal Precipitation, Maximum and Minimum Temperatures in the Southwest United States

Komlan Koudahe,Koffi Djaman,Papa Malick Ndiaye,Lamine Diop,Ansoumana Bodian

doi:10.3390/cli8120142

Komlan Koudahe, Koffi Djaman + Show 3 more

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https://doi.org/10.3390/cli8120142

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Abstract

The objective of this study is to perform trend analysis in the historic data sets of annual and crop season [May–September] precipitation and daily maximum and minimum temperatures across the southwest United States. Eighteen ground-based weather stations were considered across the southwest United States for a total period from 1902 to 2017. The non-parametric Mann–Kendall test method was used for the significance of the trend analysis and the Sen’s slope estimator was used to derive the long-term average rates of change in the parameters. The results showed a decreasing trend in annual precipitation at 44.4% of the stations with the Sen’s slopes varying from −1.35 to −0.02 mm/year while the other stations showed an increasing trend. Crop season total precipitation showed non-significant variation at most of the stations except two stations in Arizona. Seventy-five percent of the stations showed increasing trend in annual maximum temperature at the rates that varied from 0.6 to 3.1 °C per century. Air cooling varied from 0.2 to 1.0 °C per century with dominant warming phenomenon at the regional scale of the southwest United States. Average annual minimum temperature had increased at 69% of the stations at the rates that varied from 0.1 to 8 °C over the last century, while the annual temperature amplitude showed a decreasing trend at 63% of stations. Crop season maximum temperature had significant increasing trend at 68.8% of the stations at the rates varying from 0.7 to 3.5 °C per century, while the season minimum temperature had increased at 75% of the stations.

Highlights

Food production is governed by different factors, of which climate is the most important, that causes inter-annual variability in precipitation, air temperature, relative humidity and affects the socioeconomic and environmental systems related to surface and groundwater resources management and planning
A significant decrease in long-term annual precipitation was observed at Ajo and Fort Lewis (Table 2), while a non-significant decreasing trend was observed at Albany, Roosevelt, Ash Mountain, Blythe, Las Vegas, and Tonopah
Annual maximum temperature increased at 75% of the stations at the rates that varied from 0.6 to

Summary

Introduction

Food production is governed by different factors, of which climate is the most important, that causes inter-annual variability in precipitation, air temperature, relative humidity and affects the socioeconomic and environmental systems related to surface and groundwater resources management and planning. The global combined ocean and air average annual temperature has increased by 0.65–1.06 ◦ C during the 1880–2012 period [1]. A significant warming trend in annual minimum temperature and mean temperature was observed in different irrigation zones in Pakistan, while the maximum temperature showed significant variation elsewhere except at high altitudes [4]. The global mean surface temperature might increase in the range of 0.3 to 0.7 ◦ C during the 2016–2035 period compared to the 1986–2005 period under different Representative Concentration Pathways [7]. Djaman et al [10] reported a significant increase in average annual maximum and minimum air temperature and significant decrease in annual precipitation across the Senegal River valley. Men et al [11] reported that air temperature had significantly increased over the Beijing-Tianjin-Hebei region in China during the

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