Abstract:

This study investigated the characteristics of temperature and humidity variations in winter wheat fields and their quantitative relationship with observations at meteorological station. Temperature and humidity recorders were installed at heights of 10, 30, 50, 70 and 150cm in the winter wheat experimental field of Shangqiu agrometeorological observation station from October 2022 to May 2023. The spatiotemporal characteristics of temperature and humidity in the field were analyzed across different growth stages of winter wheat and different weather types. Linear regression models were developed to simulate field temperature and humidity using thermometer screen data for both the entire growth stage and different weather types. Model evaluation was conducted to enhance weather services for winter wheat production and improve agricultural meteorological service quality. The results showed that: (1) the diurnal variation characteristics of temperature and humidity at different heights during tillering−overwintering, reviving−heading and flowering−maturity stage of winter wheat were consistent with thermometer screen observations. Field temperature at all heights were 0.1−4.1°C higher than thermometer screen temperature from 7：00 to 16：00, and 0.1−3.7°C lower during other periods. Temperature peaks occurred 1−2h earlier in the field, while troughs appeared 0−1 hour earlier compared to the thermometer screen. (2) During flowering−maturity stage, humidity at heights of 50−150cm was 0.1−3.7 percentage points lower than that the thermometer screen at specific morning hours. In all other growth stages, heights and times, it consistently exceeded the thermometer screen by 0.6~26.8 percentage point. Relative humidity troughs in the thermometer screen was delayed by 1−2h compared to field. (3) The amplitude of temperature and humidity changes followed the pattern: sunny>cloudy>overcast days. Temperature differences between thermometer screen and field were 0.4°C and 0.5°C greater on sunny days than cloudy and overcast days, respectively. Similarly, relative humidity differences were 1.8 and 2.1 percentage point greater on sunny days than cloudy and overcast days. (4) The developed simulation models were approved by 0.01 level significant test on daily and hourly scales. Daily−scale simulation effect outperformed hourly−scale, and temperature modeling achieved higher accuracy than humidity, and model accuracy improved with increasing height. Model performance acrossed weather types followed a consistent hierarchy: cloudy> overcast>sunny days. 

Key words: Winter wheat, Field, Thermometer screen, Observation station, Time scale