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,**2 Y +, Z 2 [\] ,**3 Y 3 Z + [\,An Empirical Relationship between Ground-surface Temperature and Heat-discharge Rate on
Steaming Ground: Field Experiments Using IR Thermometer and Ice Box Calorimetry, ῌῌῌῌῌ
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Higashi UCHIDAῌ, Takahisa SATOῌῌ, Takatsugu YAMASHITAῌῌῌ and Akihiko TERADAῌThe heat balance model can be used to readily calculate the total heat-discharge rate through steaming groundbased on the distribution of surface temperature obtained by an infrared radiation (IR) thermometer. Thismethod is convenient ; however, the model involves some critical assumptions and large uncertainties. With theaim of developing a simple method for reliable measurements of the total heat-discharge rate, we carried out ﬁeldexperiments at the geothermal ﬁeld of Yoshioka hot springs, Aso volcano, Japan. To directly measure theheat-discharge rate at each measurement site, we used Ice Box Calorimetry (IBC), which can be used to measurethe combined conductive and convective heat-discharge rate, Q (W/m,), from the ground surface, based on thetime required to melt ice housed within an aluminum box placed on the ground. At the same time, we used anIR thermometer to measure the ground-surface temperature, T ( ), at each site. Our observations revealed therelationship between the heat-discharge rate anomaly Q ( Q Q*) and the temperature anomaly T ( TT*), where Q* and T* were the average ground-surface temperature and the average heat-discharge rate outside thegeothermal area, respectively. Although the obtained data show a degree of scatter, the value of Q increases
almost linearly with T, consistent with the heat balance model : Q C T, where C is the proportional
coe$cient, which is estimated to be /+ , (W/m,/ ) from the least squares method. We consider that thisempirical relationship is applicable in obtaining accurate estimates of the total heat-discharge rate from steaming
ground. To assess the reliability of the linear relation and determine appropriate values of C, it would benecessary to conduct additional accurate, simultaneous observations of Q and T at sites on many di#erent
volcanoes and under various meteorological conditions. Furthermore, we carried out measurements when theground surface was wet due to rainfall. As a result, we obtained Q* of ,,* W/m,, larger than the value obtainedwith a dry ground surface. This experiment suggests that the presence of rainwater enhances heat convection,
including latent heat, near the ground surface.
Key words : steaming ground, Ice Box Calorimetry, IR thermometer, heat-discharge rate, ground surface temperature 32-ῌ*2.,  +ῌ-ῌ+/ 203ῌ+.*.  !" /,2*#$%&#$'()*)*+,*-./01234*-.567
Sendai District Meteorological Observatory, Japan Mete8-.9:;<
Aso Volcanological Laboratory, Kyoto University, /,2*orological Agency (JMA), +ῌ-ῌ+/ Gorin, Miyaginoku, Sendai 32-ῌ*2.,, Japan.
Kawayo, Minami-Aso, Kumamoto 203ῌ+.*., Japan.
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Fukuoka District Meteorological Observatory, JMA,Present address. Volcanic Fluid Research Center,+ῌ,ῌ-0 Oohori, Chuo-ku, Fukuoka 2+*ῌ**/,, Japan.
Tokyo Institute of Technology, 0.+ῌ-0 Kusatsu, Gunma 203ῌ,03/ PQJ2 /*.ῌ+-11ῌ+1++, Japan.
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Aso Local Cooperative O$ce for Volcanic Disaster
Corresponding author : Higashi Uchida
Mitigation, JMA, /*.ῌ+ Miyaji, Ichinomiya, Aso, Kumae-mail : h-uchida@met.kishou.go.jp
moto 203ῌ,03/, Japan.