Two Cities at the Same Latitude
Two cities, Hama and Saka, lie at nearly the same latitude. Hama is on the coast; Saka is 80 km inland behind a mountain range. Climate records for a year show: Hama’s monthly mean temperature ranges from 9°C in February to 25°C in August; Saka’s ranges from 1°C in February to 31°C in August. Both receive about 12 hours of daylight in March and September. In June, Hama’s daily maximum occurs around 14:00, while Saka’s occurs around 15:30. A student claims the larger seasonal temperature range in Saka is caused by its being closer to the Sun in summer. Another student notes that summer winds at Hama blow from the sea toward land in the afternoon. The class also measures solar panel output: in June, a panel at Saka produces 5.8 kWh/day; at Hama, 5.6 kWh/day. In December, Saka produces 3.2 kWh/day; Hama, 2.9 kWh/day. The panel is identical and kept clean.
1. Explain why Saka has a larger annual temperature range than Hama, using the concept of specific heat capacity and the given data. Refer to at least one heat-transfer process.
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Water has a high specific heat capacity (about 4.2 J g⁻¹ °C⁻¹) compared with soil and rock (roughly 1–2 J g⁻¹ °C⁻¹). Hama is coastal, so the sea absorbs and releases a large amount of heat with only a small temperature change; maritime air also moderates the coast. Saka is inland, where the ground heats and cools more quickly and there is less water to evaporate and store heat. This explains the larger range at Saka: 1–31°C (30°C range) versus 9–25°C (16°C range). Heat transfer by radiation from the Sun affects both, but the local response differs because of heat capacity and mixing. In summer, the land heats faster than the sea, producing a sea breeze that brings cooler marine air to Hama in the afternoon. In winter, the sea is relatively warmer than the land, so maritime air can keep Hama milder. The mountain range also can shelter Saka from maritime air, increasing its continental behaviour.
2. Evaluate the claim that Saka is warmer in summer because it is closer to the Sun. Use the fact that both cities are at nearly the same latitude and the given daylight information.
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The claim is not supported. Hama and Saka are at nearly the same latitude and only about 80 km apart, while Earth–Sun distance is about 150 million km; an 80 km difference is negligible. Both cities receive about 12 hours of daylight at the equinoxes, and their solar elevation is nearly the same because latitude is nearly the same. Seasonal temperature differences are caused mainly by Earth’s axial tilt, which changes the Sun’s altitude and day length through the year, not by distance from the Sun. In fact, Earth is slightly farther from the Sun during Northern Hemisphere summer, so distance cannot explain summer warmth. The different seasonal ranges in the two cities are therefore a local climate effect: the coast is moderated by the sea’s high heat capacity, while the inland site has a more continental response. The solar-panel outputs are similar in June and lower in December at both sites, consistent with seasonal solar angle rather than a large distance effect.
3. Using the temperature data and the solar panel outputs, explain why the time of maximum temperature is later at Saka than at Hama. What role does the afternoon sea breeze play?
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Solar noon is around 12:00, but the air does not reach its maximum temperature until the ground has delivered heat to the air for several hours. The surface absorbs sunlight and warms; the air is heated mainly by contact and convection, so the peak lags. At Saka, the inland ground has a lower effective heat capacity and less evaporative cooling, so it can keep adding sensible heat into the afternoon, and the maximum occurs later, around 15:30. At Hama, the afternoon sea breeze brings cooler marine air over the land, which caps the temperature rise; the maximum is therefore earlier, around 14:00, even though the coast also has a lag. The June panel outputs are slightly higher at Saka (5.8 vs 5.6 kWh/day), consistent with fewer maritime clouds, while the December values are lower at Hama (2.9 vs 3.2 kWh/day), consistent with more coastal cloud. These local effects help explain the timing difference, but they do not support the ‘closer to the Sun’ claim.