## 2 Observing-System and Power-System Considerations
### New Observing System and Power System  
Based on the analysis of Sections 2.1 and 2.2, we designed a new observation system and power system, and adjusted the observation parameters of the sensor. The accuracy and temperature range of the sensor were fully considered. Table 1 summarizes the various sensors used in our observing system on the Arctic and Antarctic ice cover. The observing system of ice mass balance consisted of a wind-speed and a direction sensor, a temperature and humidity sensor (HMP155A, Vaisala, Vantaa, Finland), an atmospheric-pressure sensor (CS106/PTB110, Vaisala, Vantaa, Finland), and a 10 m long thermistor string and two spectroradiometers (TriOS, TriOS Optical Sensors, Oldenburg, Germany). The wind-speed and direction sensor was developed by TYUT, designed to overcome the effects of frozen environments by relying on self-heating strings around the sensor. The 10 m long thermistor string was also designed by TYUT and successfully observed the temperature profiles of shallow ice cover.  
As shown in Figure 5, the power-supply system of the observing system of the ice mass balance involved in this study is equipped with a power generator that includes the PV array and small wind turbine (SWT), an energy-storage system (a low-temperature battery pack), an end user (load), and a control station (hybrid wind-solar charging circuit). The whole power system is a standalone system. This power-supply system was specifically designed for our small ice mass-balance station. In the design process of the hybrid wind-solar charging circuit, three subcircuits were developed: (1) SWT charging circuit: A three-phase rectifier circuit is required to convert the three-phase alternating current generated by the small wind turbine into a stable direct current. After the rectified and filtered direct current passes through the chopper circuit, it becomes a stable direct current and supplies power to the load or the battery. (2) Solar charging circuit: It is necessary to design a suitable DC chopper circuit and implement the control strategy for the solar charging circuit by adjusting the conversion circuit. (3) Detection circuit and ADC circuits: These subcircuits are mainly used to monitor solar-battery voltage and current, SWT voltage and current, battery voltage, and charging current.  
Battery capacity generally decreases at lower ambient temperatures. Therefore, the capacity of battery at low-temperature ranges (\(-\)50-30 \({}^{\circ}\)C) should be completely understood to make the observing system work properly and stably. The performance of the ADC, detection, and auxiliary circuits at low temperatures should be considered, which may affect the charging strategy of the charging circuit.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sensor Name** & **Performance** & **Sensor Model** \\ \hline \multirow{2}{*}{Wind speed} & Temperature range: \(-\)60–30 \({}^{\circ}\)C & \multirow{2}{*}{TYUT} \\  & Accuracy: 0.5 m/s & \\ Wind direction & Temperature range: \(-\)60–30 \({}^{\circ}\)C & \\  & Accuracy: 0.3\({}^{\circ}\) & \\ Air temperature & Temperature range: \(-\)60–10 \({}^{\circ}\)C & \\  & Accuracy: 0.1 \({}^{\circ}\)C & \\ Humidity & Temperature range: \(-\)60–10 \({}^{\circ}\)C & \\  & Accuracy: 2\({}^{\circ}\)RH & \\ Atmospheric & Temperature range: \(-\)60–30 \({}^{\circ}\)C & \\ pressure & Accuracy: 0.6 hPa & \\ Thermistor string & Temperature range: \(-\)60–30 \({}^{\circ}\)C & \\  & Accuracy: 0.1 \({}^{\circ}\)C & \\ Spectroradiometer & Temperature range: \(-\)60–30 \({}^{\circ}\)C & \\  & Accuracy: 5\% & TriOS, TriOS Optical Sensors, Germany \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sensor information of the observing system.