实际上，您需要的是z值和零值的交点坐标。
我从这个答案中借用了代码：在Python中以高精度查找由（x，y）数据给出的两条曲线的交点
在您的示例中，函数interpolated_intercept中的三个参数为：

x --> y_node (which is the grid coordinated y)
y1 --> z_axis_y (z values along the y-axis)
y2 --> z_zero (an array of zeros has the same size with z_axis_y)

下面是完整的代码：

import matplotlib.pyplot as plt
import numpy as np

def interpolated_intercepts(x, y1, y2):
    """Find the intercepts of two curves, given by the same x data"""

    def intercept(point1, point2, point3, point4):
        """find the intersection between two lines
        the first line is defined by the line between point1 and point2
        the first line is defined by the line between point3 and point4
        each point is an (x,y) tuple.

        So, for example, you can find the intersection between
        intercept((0,0), (1,1), (0,1), (1,0)) = (0.5, 0.5)

        Returns: the intercept, in (x,y) format
        """    

        def line(p1, p2):
            A = (p1[1] - p2[1])
            B = (p2[0] - p1[0])
            C = (p1[0]*p2[1] - p2[0]*p1[1])
            return A, B, -C

        def intersection(L1, L2):
            D  = L1[0] * L2[1] - L1[1] * L2[0]
            Dx = L1[2] * L2[1] - L1[1] * L2[2]
            Dy = L1[0] * L2[2] - L1[2] * L2[0]

            x = Dx / D
            y = Dy / D
            return x,y

        L1 = line([point1[0],point1[1]], [point2[0],point2[1]])
        L2 = line([point3[0],point3[1]], [point4[0],point4[1]])

        R = intersection(L1, L2)

        return R

    idxs = np.argwhere(np.diff(np.sign(y1 - y2)) != 0)

    xcs = []
    ycs = []

    for idx in idxs:
        xc, yc = intercept((x[idx], y1[idx]),((x[idx+1], y1[idx+1])), ((x[idx], y2[idx])), ((x[idx+1], y2[idx+1])))
        xcs.append(xc)
        ycs.append(yc)
    return np.array(xcs), np.array(ycs)


# Load the 3D data file
data = np.genfromtxt("Ta_parameterspace_2mm.txt", skip_header=14, delimiter="\t", dtype = float)
#print(data)
reflect = data[:,0]
emiss = data[:,1]
tempdiff = data[:,4]

# Find the node list for x and y 
x_node = np.unique(reflect)
y_node = np.unique(emiss)

# Initialization of a array of 0 
z_zero = np.zeros(len(y_node))

# Reshape the tempdiff 
z_values = tempdiff.reshape(40, 40)

# Find the intersection between the z values along the axis y and 0 
x_intersection = []
y_intersection = []

for idx in range(len(z_zero)):
    z_axis_y = z_values[idx, :]
    y_inter_temp, _ = interpolated_intercepts(y_node, z_zero, z_axis_y)
    # Only if there is an intersection 
    if len(y_inter_temp) >0:
        x_intersection.append(x_node[idx])
        y_intersection.append(y_inter_temp[0][0])
    

fig, ax = plt.subplots()
cb = ax.tricontourf(reflect, emiss, tempdiff, 200, cmap = "seismic")
cbar = plt.colorbar(cb)
cbar.set_label('Temperature (K)', rotation = 270, labelpad = 13)
ax.set_xlabel('Reflectivity')
ax.set_ylabel('Emissivity')
plt.plot(x_intersection, y_intersection, 'k-*')
plt.show()

然后你得到的数字：