Week 9 frost assignmnet

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Melbourne Business School *

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Mathematics

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Apr 3, 2024

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Week 9 Frost work Group 2 1266434 You Lyu 1166108 Yueer Xu 1166166 Huiwen Wang 1253484 Charli Anderson 1168825 Raymond Martin Activity 1 Question 1 Describe the difference(s) between radiation frost and advection frost. Which is more common in Australia? radiation frost occurs on cold, clear, nights with no wind, when objects can cool rapidly by radiating out to the open air, and advective frost occurs when a cold air mass suddenly moves into a moisture-rich warmer region. Therefore radiation frost is common in Australia. Question 2 Why is the risk of radiation frost greater under clear skies when there is little or no wind? Under clear skies and lower winds, the ground absorbs more heat from the sunlight throughout the day. When this heat is radiated back into the atmosphere, there is more heat energy radiated back into the atmosphere, hence creating a greater risk of radiation frost. Activity 2 Question 3 What do the instruments in the Stevenson screen measure? The instruments within the stevenson screen measure levels of heat radiation, heat, precipitation, water vapor levels, air pressure, etc. Question 4 How do these instruments relate to predicting the risk of frost occuring? The instruments within the stevenson screen register the temperature, the air pressure, etc. As a general indicator, temperature thresholds of 2C or below indicate a possibility of frost. Activity 3 Question 5 Identify the areas of this field that would be more susceptible to frost and why that is the case. Use information provided by the Food and Agriculture Organisation (FAO) of the United Nations for your reasoning: http://www.fao.org/docrep/008/y7223e/y7223e0c.htm#bm12.1.2 For figure 6.4, the lower spots of the topological profile are more susceptible to frost as there is more cold air drainage at lower spots. Question 6 Can you think of some possible methods that might protect your crops from frost? In what way(s) would these methods work?

Week 9 Frost work Cliffs, rocky masses, canopy covers, trees, plants, etc can all increase downward night time radiation and increase minimum temperatures. Remove all obstacles that inhibit down slope drainage and level the land. Certain soil types are known to be less prone to frost. Question 7 If your field has a high soil moisture content, would this be more or less prone to a radiation frost risk compared to a dry, rain fed field? How does soil does moisture affect the chance of frost occurring? Soil type determines the amount of energy stored in the soil, as well as the amount of energy released. Question 8 Consider the top 10 cm of soil in a field (κ = 1.82 W m-1 K-1 ) for a small trial plot with surface area of 1.5 m2. How much heat is conducted through the soil if the soil temperature is 15°C and the air temperature is 1 °C? Activity 4 Question 9 Describe what you found out about the dry matter intake of the ewes. Why do you think this is the case? The dry herbage intake has a mean of approximately 1722.7g per day with a standard deviation of 201.4 Question 10 Describe what you found out about the clean wool growth of the ewes. Why do you think this is the case? The clean wool growth post shearing has a mean of 0.4165 mg cm with a standard deviation of 0.163. Question 11 Describe what you found out about the weight of the lambs at birth. Why do you think this is the case? The weight of the lambs at birth has a mean of 4.25kg with a standard deviation of 0.1975. Question 12 Was there any difference in the mortality of the ewes. Why do you think this is the case? There seems to be no correlation between the mortality of the ewes and any other of the variables provided. Question 13 Consider a sheep with a 2 cm fleece (κ= 5.91 x 10-4 W m-1 K-1 ) and a surface area of 1.5 m2 . How much heat is conducted through the fleece if the sheep’s skin temperature is 25°C and the air temperature is 12 °C ?

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