| Based on the experimental data,the regulation effect of greenhouse on air temperature and relative humidity in grape growing period was studied,and a prediction model of the hour-by-hour air temperature and relative humidity inside the greenhouses was established by stepwise regression method.The following conclusions were drawn:(1)Rest Period: In the early stage,the temperature inside and outside the greenhouse was the same between sunny days and cloudy days at 7:00-8:00 and 16:00-17:00,and the maximum temperature drop inside the greenhouse was >4.0? at night.In the morning,the temperature outside the greenhouse increase most obviously when it was between 6.0? and 10.0?,and the maximum temperature increase was 6.7?and 7.0?,respectively in typical sunny days and cloudy days.In the middle stage,the temperature outside the greenhouse was-8.9?-6.2? from the early morning of a typical day after the external temperature was cooled,and temperature inside the greenhouse increased 5.3?6.3?,while the temperature in other periods was always stable at3.3?5.2?.In the period of temperature outside the greenhouse before cooling,the greenhouse has no evident regulation effect on air temperature.In the later period,the temperature outside the greenhouse on a typical sunny day was between-10.4? and0.3?,and the temperature inside the greenhouse increased from 7.3? to 8.9? stably at night,while the temperature inside the greenhouse increased from 8.6? to 19.2?during the day and then decreased.The temperature outside the greenhouse increased most significantly when the temperature was around 0? at noon.On a typical overcast day,the temperature outside the greenhouse was-5.3?0.9?,and the temperature inside the greenhouse was 5.3?15.2?.When the temperature outside the greenhouse was-0.2?0.9? around noon,the temperature inside the greenhouse was relatively high,and the temperature inside the greenhouse in other periods was <7.0?.There is a high probability of low temperature disaster outside the greenhouse during the whole rest period,but there is no risk of disaster inside the greenhouse.(2)Pregermination Period: In typical sunny and cloudy days,when temperature outside the greenhouse at night varied between-10.0?-1.0?,temperature increment inside the greenhouse was 8.0?10.0?.During the daytime,the temperature outside the greenhouse was between-1.0?-4.0?,and the temperature increment on sunny days was slightly higher than on cloudy days.When temperature outside the greenhouse was around 12.0?21.0?,the temperature increment inside the greenhouse on sunny days were slightly higher than on cloudy days.On a typical overcast day,when the temperature outside the greenhouse was between 1.0?2.0? around noon,the temperature inside the greenhouse increased between 10.3?14.7?.When the temperature outside the greenhouse was between-5.0?0?,the temperature inside the greenhouse increased between 7.0?10.0?.The highest temperature inside the greenhouse was 24.7? on sunny days >20.6? on cloudy days >16.6? on overcast days.The lowest temperature inside the greenhouse was 0.7? on sunny days <2.7?on cloudy days <4.4? on overcast days.The air relative humidity outside the greenhouses is low and fluctuated greatly,but the humidity inside the greenhouses is high and stable.Most of the greenhouses are in a nearly saturated state of over 95% at night,and the air relative humidity in the daytime is >50%.(3)Germination Period and Early Shooting Period: In typical sunny and cloudy days,when temperature outside the greenhouse varied between 0.7?3.2? and 7.7?1.1?respectively,temperature increment inside the greenhouse was 4.0?16.0? and11.0?14.0?.The temperature outside the greenhouse was 1.7?2.8? and 2.5?5.2?respectively before ventilation.During this time,the greenhouse temperature increment was the most significant,and the temperature increase is 24.9?25.9? and 20.7?23.0?respectively on sunny and cloudy days.On a typical cloudy day,the temperature variation outside the greenhouse was 3.9?2.3?,and temperature increase inside the greenhouse was relatively stable throughout the day.The greenhouse temperature increase was slightly lower around 9.0? in the morning and slightly higher around14.0? in the afternoon.The temperature was 6.0?28.7?,6.4?25.9? and 7.1?16.4?,on typical sunny,cloudy and cloudy days respectively.There was slight difference in minimum temperature under the three weather patterns,but the maximum temperature was significantly lower on overcast days.In the germination period and early shooting period,the relative humidity in the greenhouse is basically the same as that in the germination stage,although in rare cases,the humidity inside the greenhouse was reduced when the relative humidity outside the greenhouse is too high,while the humidity inside the greenhouse maintained the same level with that of pregermination period.(4)Blossom and Fruit Period: In the morning of a typical sunny day and cloudy day,the temperature increment in the greenhouse was the most obvious at 10.0?13.0?,when temperature outside the greenhouse were between 10.0?13.0?,and 15.0?16.5?.The temperature increment inside the greenhouse was <8.5? at night.Temperature outside the greenhouse was >10.0? during most periods of a typical cloudy day,but the temperature inside the greenhouse was <8.0? throughout the day.The minimum temperature increment inside the greenhouse was 5.3? on sunny days > 3.1? on cloudy days > 0.7? on overcast days typically.Maximum temperature increment inside the greenhouse was 12.8? on sunny days > 12.5? on cloudy days > 7.7? on overcast days typically.The lowest temperature in the greenhouse was around 12.0?,and the highest temperature was 28.3? on cloudy days > 26.1? on sunny days > 23.5? on overcast days typically.Due to the obvious humidification effect of greenhouses,the relative humidity at nights were 90% and 80% respectively on sunny days and cloudy days,while <50% during the daytime.The relative humidity of overcast days are maintained at 70% ? 90% the all day.(5)Fruit Developing Period and Fruit Ripening Period: Air temperature inside the greenhouse dropped at night and increased during the day,thus effectively expanded the temperature difference between day and night.The temperature inside and outside the greenhouse is the same between 5:00-7:00 and 18:00-20:00.The temperature in the greenhouse decreased ?2.0? at night and increased ?7.9? during the day in typical sunny,cloudy and overcast days.There is little difference in the regulation effect of greenhouse under the three weather patterns.The daily temperature difference in the greenhouse was 17.9?,12.6? and 12.9? respectively under the three weather patterns after regulation,which are about twice as much as outside the greenhouse.(6)Under the control of the greenhouse,the maximum air temperature inside the greenhouse is generally 1?2h earlier than the outside of the greenhouse.Most of the maximum air temperature increase inside the greenhouse is synchronized with the appearance of the maximum temperature inside the greenhouse,and the difference in the minimum temperature is small.The risks of disaster-causing air temperature and air relative humidity outside the greenhouse during each growing period are relatively high.The probability of occurrence of disaster-causing air temperature inside the greenhouse during blossom and fruit period and fruit developing and ripening period is about 20%.In other cases,the disaster-causing air temperature and air relative humidity basically did not appear inside the greenhouse.(7)The root mean square error(RSME)of air temperature forecasting modeled value and the measured value was ?3.7 ?,and the mean absolute error(MAE)was?2.9 ?.The root mean square error(RSME)of air relative humidity forecasting modeled value and the measured value was ?13.3%,and the mean absolute error(MAE)was ?10.6%.The forecast result of air temperature was accurate,but the forecast result of air relative humidity was inferior. |
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