• 论文与研究报告 •

### 帽儿山两林分气温与地表可燃物温度差异及对可燃物含水率预测的影响

1. 东北林业大学林学院 哈尔滨 150040
• 收稿日期:2014-12-30 修回日期:2015-04-14 出版日期:2015-07-25 发布日期:2015-08-14
• 通讯作者: 金森
• 基金资助:

国家自然科学基金项目(31370656)。

### Differences of Air Temperature and Fuel Surface Temperature in Two Stands in Maoershan Forest Farm and Their Effects on Fuel Moisture Modelling

Yang Bowen, Chen Pengyu, Jin Sen

1. College of Forestry, Northeast Forestry University Harbin 150040
• Received:2014-12-30 Revised:2015-04-14 Online:2015-07-25 Published:2015-08-14

[目的] 对不同地区地表可燃物温度与气温的差异、气温-可燃物温度转换模型在不同地区的适用性以及应用气温和地表可燃物温度分别驱动直接估计法模型的误差进行研究,为提高可燃物含水率预测精度提供参考。[方法] 在东北林业大学帽儿山试验林场红松和落叶松2个林分下,采用自动气象站测量距地表1.5 m处气温,采用热电偶测量距地表1,2,3,4 cm处地表可燃物温度。红松林分共观测10天,落叶松林分共观测4天,其中,1天在每个林分中设置2个采样点,对距地表1 cm的可燃物含水率每隔1 h测定1次。对气温和地表可燃物温度的差异进行比较,计算目前在可燃物含水率预测中常用的2个气温-地表可燃物温度转换模型(Byram & Jemison模型和Van Wagner模型)的预测误差,根据误差对其适用性进行评价。以目前常用的基于时滞和平衡含水率的可燃物含水率直接预测法为例,分析这2个模型其对可燃物含水率直接估计法精度的影响。[结果] 1) 地表可燃物温度与气温有差异,白天低于气温,夜间高于气温;2) 现有2个气温-地表可燃物温度转换模型的误差大于3℃,不能反映气温和地表可燃物温度之间白天和夜间的异向差异;3) 在可燃物含水率的直接估计法模型中,采用气温作为温度变量和采用通过气温-可燃物温度转换模型计算所得的可燃物温度作为温度变量所建立的模型效果相似。[结论] 现有的2个气温-可燃物温度转换模型所计算的可燃物温度都高于气温,误差很大,在研究地区不适合用于计算地表可燃物温度。对于以时为步长的可燃物含水率直接估计模型,无需利用现有气温-可燃物温度转换模型进行温度转换。利用气温建模还是利用地表可燃物温度建模的优劣目前尚无法确定,需进一步研究。研究新的可燃物温度模型,特别是能够反映气温和可燃物温度差异日变化的转换模型,将是未来研究的任务。

Abstract:

[Objective] Temperature is an important factor affecting fuel moisture and is frequently used for fuel moisture prediction. Fuel surface temperature is used in physical or quasi-physical moisture models instead of air temperature, thus, a conversion from air temperature to fuel surface temperature is required. Currently commonly used conversion models such as Byram & Jemison mdoeland Van Wagner model are statistically based models with varied applicability at different regions. In this study, we intend to answer following questions: 1) What are differences between air temperature and fuel surface temperature at different areas? 2) How about the applicability of these conversion models at different regions? 3) What is the deviation of fuel moisture prediction using these conversion models? [Method] Air temperatures at 1.5 m height in a Korean pine stand and a larch stand were measured using a automatically weather station in Maoershan Forest Farm in Harbin, Heilongjiang Province. The fuel surface temperatures at 1, 2, 3 and 4 cm above ground surface were measured at the same time using thermocouples. Temperature observation was conducted for ten days in the Korean pine stand and four days in the larch stand. Moisture contents of the fuels at 1 cm above surface ground were monitored at 1h intervals at two sites in each stand for a successive 24 h. Comparison of air temperature and fuel surface temperature at different heights were conducted. Deviation of fuel surface temperature computed using the two conversion models was evaluated. Applicability of the two models was assessed based on the deviation. Influences of conversion of fuel surface temperature from air temperature using the two models on direct estimation accuracy of fuel moisture via a model proposed by Catchpole et al. were evaluated. [Result] 1) There exist differences between air temperature and fuel temperature, that is, fuel temperature is lower than air temperature in daytime but higher at night. 2) The two conversion models have deviation of more than 3℃, however it cannot reflect the bidirectional differences of air temperature and fuel temperature at daytime and night. 3) Models for direct estimation of fuel moisture established using air temperature and using fuel temperature calculated from the two conversion models have similar accuracy. [Conclusion] Temperature computed from the two conversion models is higher than the measured values in field with much greater deviation, indicating that temperature conversion is not suitable in this study area. It is not necessary to convert air temperature to fuel temperature, but using air temperature directly at 1h intervals for direct estimation of fuel moisture. It can still not determine which one is better to establish fuel moisture mode by using air temperature or fuel surface temperature and further investigation is required. Another important task for future research is developing new temperature conversion models which can truly reflect daily differences between air temperature and fuel surface temperature.